Stage a Coup to become king of the hill!

Question

Leaderboard

  154 Calculator
  144 Taxman
  138 Statistician
  137 Solver
  137 RandoAggroLawyer
  136 Gambler
  134 Turncoat
  119 Lawyer
  119 BloodyMurder
  113 Bandit
   79 Challenger
   74 Mask
   64 Random

An archive of the latest match, including the log and all output files, is available.

Calculator, by Brilliand, is the winner! His answer is accepted, but that doesn't mean the challenge is over. Feel free to submit new entries or edit your current ones and try to knock him off his throne. I will award a bounty to the leader at the end of the month.

Rules of Play

Coup is a card game designed for 2-6 players, which we shall play with two. It consists of a treasury of coins (infinite for our purposes) and a deck of 15 cards, containing 3 each of the following types: Ambassador, Assassin, Captain, Contessa, Duke. At the start of the game, each player is given one coin and dealt two cards at random, which they keep secret until necessary. The object is to be the last player with cards in your hand.

On their turn, a player may take one of the following actions regardless of their cards:

• Income: take 1 coin from the treasury. Unblockable and unchallengeable.
• Foreign Aid: take 2 coins from the treasury. Can be blocked by a player with a Duke. Unchallengeable.
• Coup: Remove a card of one opponent of your choice from play. Costs 7 coins. The victim may choose which card to discard. If a player has 10 or more coins at the start of their turn, they must Coup. Unblockable and unchallengeable.

Depending on their cards, players may also take one of the following actions as their turn:

• Exchange: a player with an Ambassador may take two cards from the deck. Then they may choose from their hand and the drawn cards as many cards as they originally had. (That is, if they had only one card they may exchange it for one of the drawn cards or keep it, and if they had two cards they may choose any two of the four cards.) The two undesired cards are returned to the deck. Unblockable, but challengeable.
• Assassinate: a player with an Assassin may spend 3 coins to remove an opponent's card from the game. The victim may choose which card to discard. Can be blocked by a player with a Contessa, in which case the coins are not returned. Challengeable, in which case the coins are returned.
• Steal: A player with a Captain may take two coins from their opponent. If the opponent has one coin, they will take that one coin. If the opponent has zero coins, they may not Steal. Can be blocked by a player with an Ambassador or a Captain. Challengeable.
• Tax: A player with a Duke may take 3 coins from the treasury. Unblockable, but challengeable.

The tricky part of Coup is that players are allowed to lie about what cards they have! One need not have a card to attempt to perform the action or block associated with it.

When a player performs a card's action, any opponent (even one who is not harmed by that action) may challenge the actor and say they do not believe they have the card for that action. If the challenger is correct, the action is cancelled and the actor must discard one card of their choice (gaining back any coins they spent if applicable). If not, the action is taken, the actor returns the card they were challenged about to the deck and draws a new one, and the challenger must discard one of their cards. Players must be truthful about what cards they hold when challenged.

Cards eliminated from play with Assassinate, Coup, and lost challenges are not returned to the deck, but cards revealed as part of a won challenge are returned to the deck.

Blocks may be challenged just like actions. For example, if player A claims Foreign Aid and player B says "I have a Duke and I block your Foreign Aid", A may say "I don't believe you have a Duke." If that assertion is correct, B loses a card for being caught in a lie and A takes 2 coins; if it is not, A loses a card and gets no coins, and B must return their Duke to the deck and draw a new card.

The way blocks and challenges work with Assassinate must be fleshed out. Suppose Player A says "I have an Assassin, and I Assassinate Player B". If B does not attempt to challenges or blocks A, then the assassination goes through: B loses a card and A pays 3 coins.

Alternatively, B can challenge by saying "I don't believe you have an Assassin". If that is true, then A discards a card and their coins are returned, while B is unaffected, and A's turn ends. If B's belief is incorrect and A holds an Assassin, then B loses both their cards and fails, one for the incorrect challenge and one from the Assassination.

Instead of challenging, B could say "I have a Contessa, and I block the Assassinate". If A believes B, then A's turn ends and their coins are not returned. But A can challenge the block and say "I don't believe you have a Contessa." If B does in fact hold a Contessa, then A loses a card for the incorrect challenge. But if B does not, then B loses one card for being caught in a lie and another from the Assassination.

Similar logic to the above explanation applies to the Captain’s Steal ability, where either the action or the block can be challenged.

It is possible to lose both your cards and be eliminated in one turn, if you unsuccessfully challenge an Assassinate or you are caught falsely claiming you have a Contessa to block an Assassination. You lose one card from the challenge and one card from the Assassination.

Challenge

Your task is to write a program that will play Coup. It will be given as its command line arguments:

• The name of a file containing the list of its and its opponents' actions so far.
• An integer from 0 to 12 indicating the opponent's coin count.
• An integer from 0 to 12 indicating its coin count.
• A string from one to four characters long indicating its cards. Normally this will simply be the one or two cards your program has, but if your program has just succeeded at an Exchange, it will be n + 2 characters long, where n is your number of cards remaining. Your program must then output the n cards it wishes to keep to STDOUT. (Programs must not read or access STDOUT other than for this purpose — if you wish to produce debug output, please write to STDERR.)
• One or more arguments indicating the legal moves it may make.

(Example invocation: yourprogram file.txt 1 7 '~!' a c p q, meaning "Your opponent has 1 coin. You have 7 coins, an Ambassador, and a Contessa. Write to file.txt your choice of a, c, p, or q given the game history and current game state.")

Your program must append one or (in two specific situations) two characters to the provided file indicating its action. It must not otherwise alter the existing contents of the file. It may create any new files it wishes, but only within the directory in which it is run. Please provide all necessary commands to compile and run your program.

I have provided two example competitors below, written in Go.

The output format is:

• I\n: Income. Legal responses: any turn action (assuming one has the coins for Assassinate/Coup).
• F: Foreign aid. Legal responses: d (block as a Duke), p (let it pass).
• C: Coup. Legal responses: whichever of _, ', <, =, 0 is in your hand.
• E: Exchange. Legal responses: q (challenge, not believing the player has an Ambassador), p.
• T: Tax. Legal responses: q (challenge, not believing the player has a Duke), p.
• A: Assassinate. Legal responses: s (block as a Contessa), q (challenge), and whichever of _, ', <, =, 0 is in your hand.
• S: Steal. Legal responses: a (block as an Ambassador), c (block as a Captain), q (challenge, not believing the player has a Captain), p.
• d: block Foreign Aid as a Duke. Legal responses: \n (accept the block), q (challenge, not believing the player has a Duke).
• a: block a Steal as an Ambassador. Legal responses: \n (accept the block), q (challenge, not believing the player has an Ambassador).
• c: block a Steal as a Captain. \n (accept the block), q (challenge, not believing the player has a Captain).
• s: block an Assassinate as a Contessa. Legal responses: \n (accept the block), q (challenge, not believing the player has a Contessa).
• p: pass challenging an Exchange/Tax/Steal when it is not your turn. Not used with A; to decline to challenge an Assassination write one of _'<=0. Legal response: \n (end your turn), and if you have just succeeded at an Exchange, writing the cards you wish to keep from the fourth command line argument to STDOUT.
• q: challenge the most recent action or block. Legal response: if you have the card for the action that was challenged, whichever of ~^*!$ it was. If you don't, then whichever of _'<=0 from your hand which you wish to give up, followed by a newline if and only if it is your turn.
• ~, ^, *, !, $: reveal that you were telling the truth about holding, respectively, an Ambassador, an Assassin, a Captain, a Contessa, and a Duke (also used to represent these cards in command line arguments, and STDOUT output in an Exchange). Legal responses: whichever of _, ', <, =, 0 you have in your hand.
• _, ', <, =, 0: give up as punishment, respectively, an Ambassador, and Assassin, a Captain, a Contessa, and a Duke because you lost a challenge or were Assassinated/Couped. Legal response: \n.
• \n: end your turn, in doing so declining to challenge a block if applicable. Legal responses: any capital-letter action (assuming one has the coins for Assassinate/Coup and the opponent has the coins for Steal).

The format has the following useful properties:

• Turns begin with a capital letter.
• Lines follow the pattern: uppercase letter, lowercase letters, optionally punctuation marks or 0 for revealed cards, newline.
• A file ending with a newline, or an empty file, indicates that it is the start of your program's turn and it must choose a capital letter action.
• The legal actions you are allowed to take on an invocation are usually uniquely determined by the last character in the file. The exception is q, which will have some logic associated with it. See the function get_legal_actions in the arbiter to help understand this. Or you can just use the legal actions you're given on the command line.
• An even number of characters on a line indicate that the turn is yours and your program is asked to choose an action, challenge a block, or end its turn.
• An odd number of characters on a line indicate that the turn is not yours and your program is asked to block, challenge, or reveal/surrender a card.

I will give an example for every action.

I\n is the easiest to understand. A program takes one coin of Income, then ends its turn. This is one of the two cases where programs must print two characters, as Income is the only action where the opponent is both unaffected and cannot block or challenge.

Fp\n means that one program took Foreign Aid, then its opponent declined to block (p). On its next invocation, the first program noted that by the final lowercase p and/or the even number of characters on this line it took this turn, which has not ended yet, so it knows to end its current turn by printing a newline.

C=\n means that one program launched a Coup. Its opponent, knowing that it was called to react by the odd number of letters on the line, gave up a Contessa. Again, the first program knew that this was its incomplete turn on its next invocation by the even number of characters on the line, so it wrote a newline to end its turn.

Eq~<\n would mean that one program attempted an Exchange (E) and its opponent challenged (q). The Exchanging program revealed that it truthfully had an Ambassador (~) and the challenger gave up a Captain as punishment (<). After the challenger exits, the Exchanging program is invoked again with a four-character string as its fourth command-line argument (or three characters, if it had only one card). It writes the characters representing the cards it wishes to keep to STDOUT and a newline to the file.

Tq'\n means that one program attempted an untruthful Tax, was challenged, and gave up an Assassin. It illustrates the other case where two characters are written: if it is your turn and you are forced to give up a card — either from an opponent's correct challenge (as here) or from your incorrect challenge of a block — then you must write both the card you give up and a newline to end your turn.

Asq!'\n would mean that Player B attempted to Assassinate player A (A), but A claimed to have a Contessa to block it (s). B did not believe A and challenged (q). A revealed that they did, in fact, have a Contessa (!). B gave up an Assassin as punishment, losing their coins, and ended their turn ('\n), writing two characters as in that special case. (If A had decided not to block or challenge, it could have written =, and then its opponent would have seen that the turn was over and written a newline. The line would then have read A=\n, like the Coup example.)

Sq*0\n means that one program attempts a Steal; the opponent challenges, not believing the thief has a Captain; and the original program reveals a Captain, so the challenge is unsuccessful and the challenger gives up a Duke as punishment. (Another option for its opponent would be to accept the Steal by writing p. Its opponent would then detect the end of its turn and write \n, resulting in a line of Sp\n.)

The Arbiter

Programs will be invoked by this Python script. It conducts ten rounds, in which every competitor faces every other competitor while going both first and second. It tracks cards and coin counts and determines the loser by the first program to end a line with a punctuation mark twice. Programs that exit with a non-zero status, modify the file, write an illegal move to the file, or attempt an illegal Exchange will automatically forfeit. If each player takes more than 100 actions, including blocks and challenges, with no winner, then both programs lose. A winner is granted one point. The player whose program scores the most points wins.

I suggest you read the Arbiter's source code, especially the get_legal_actions function. It may help you understand the specification and write your own programs.

import itertools
import os
import random
import subprocess

class Player:
    def __init__(self, name, command):
        self.name = name
        self.command = command
        self.score = 0
        self.coins = 1
        self.cards = ""

actions_dict = {
    'E': '_', 'T': '0', 'A': "'", 'S': '<',
    'd': '0', 'a': '_', 'c': '<', 's': '='
}
punishment_to_reveal = {'_': '~', "'": '^', '<': '*', '=': '!', '0': '$'}
reveal_to_punishment = {
    punishment_to_reveal[k]: k for k in punishment_to_reveal
}

def get_legal_actions(history, player, opponent):
    c = history[-1]
    result = ""
    # Our turn begins; choose an action.
    if c == '\n':
        if player.coins >= 10:
            return ["C"]
        ret = ['I\n'] + list("FET")
        if player.coins >= 3:
            ret.append("A")
        if player.coins >= 7:
            ret.append('C')
        if opponent.coins > 0:
            ret.append("S")
        return ret
    # Opponent attempted foreign aid; can pass or claim Duke to block.
    elif c == 'F':
        return list('dp')
    # We have been Couped; must surrender a card.
    elif c == 'C':
        return player.cards
    # We failed a challenge; must surrender a card and print a newline
    # if it is our turn.
    elif c in '~^*!$':
        if history[-3] in 'acds':
            return [card + '\n' for card in player.cards]
        return player.cards
    # Opponent attempted Exchange or Tax; can pass or challenge.
    elif c == 'E' or c == 'T':
        return list('pq')
    # Opponent attempted an Assassination; can block, challenge, or give in.
    elif c == 'A':
        return list('sq') + player.cards
    # Opponent attempted to Steal; can pass, block as Ambassador/Captain,
    # or challenge.
    elif c == 'S':
        return list('acpq')
    # Opponent blocked; can challenge or withdraw.
    elif c in 'acds':
        return list('q\n')
    # Opponent passed on blocking Foreign Aid/Tax/Exchange or they gave up a
    # card as punishment, must end turn.
    elif c in "p_'<=0":
        return ['\n']
    # Opponent challenged us.
    elif c == 'q':
        challenged_action = history[-2]
        # If we have the card they challenged us over, must reveal it.
        necessary_card = actions_dict[challenged_action]
        if necessary_card in player.cards:
            return [punishment_to_reveal[necessary_card]]
        # Otherwise, we can give up either of our cards, writing a newline
        # if it is our turn.
        if challenged_action in 'acds':
            return list(player.cards)
        else:
            return [card + '\n' for card in player.cards]
    else:
        return None

deck = ['_', "'", '<', '=', '0'] * 3
random.shuffle(deck)

def determine_turn_effects(line, output, cards, current_player, opponent):
    last_action = line[-2]
    # Only operate if the opponent declined to challenge (p) or the
    # program successfully challenged their block
    if last_action in "p_'<=0":
        primary_action = line[0]
        # Foreign Aid
        if primary_action == 'F':
            print current_player.name, "received 2 coins of Foreign Aid"
            current_player.coins += 2
        # Tax
        elif primary_action == 'T':
            print current_player.name, "received 3 coins of Tax"
            current_player.coins += 3
        # Steal
        elif primary_action == 'S':
            stolen_coins = 1 if opponent.coins == 1 else 2
            print current_player.name,\
                    "stole %d coins from %s" % (stolen_coins, opponent.name)
            current_player.coins += stolen_coins
            opponent.coins -= stolen_coins
        # Exchange, store desired cards and replace undesired ones
        elif primary_action == 'E':
            print current_player.name, "tried to take %r" % output, "from", cards
            legal_outputs = [''.join(p) for p in itertools.permutations(
                    cards, len(current_player.cards))]
            if output not in legal_outputs:
                print current_player.name, "forfeits by illegal exchange"
                return opponent
            current_player.cards = [
                reveal_to_punishment[c] for c in output
            ]
            undesired_cards = list(cards)
            for c in output:
                undesired_cards.remove(c)
            for card in undesired_cards:
                deck.append(reveal_to_punishment[card])
            random.shuffle(deck)
    # Coins are not returned from a successful Contessa block
    elif last_action == 's':
        print current_player.name, "lost 3 coins from a Contessa block"
        current_player.coins -= 3
    return None

def play_game(player1, player2, round_number, game_number):
    outfilename = os.path.abspath(__file__)[:-len(__file__)] + '_'.join([
        player1.name, player2.name, str(round_number), str(game_number)
    ]) + '.txt'
    print outfilename
    f = open(outfilename, 'w')
    f.close()
    players_list = [player1, player2]
    player1.cards = [deck.pop(), deck.pop()]
    player2.cards = [deck.pop(), deck.pop()]
    current_player_index = 0
    for i in range(200):
        current_player = players_list[current_player_index]
        opponent = players_list[(current_player_index+1) % 2]
        legal_actions = []
        original_contents = []
        original_contents_joined = ""
        with open(outfilename, 'r') as outfile:
            original_contents = outfile.readlines()
            original_contents_joined = ''.join(original_contents)
            if len(original_contents) == 0:
                legal_actions = ['I\n'] + list("FEST")
            else:
                legal_actions = get_legal_actions(
                        original_contents[-1], current_player, opponent)
        if not legal_actions:
            print "Error: file ended in invalid character"
            return current_player
        # Has the player completed an Exchange? Pass them new cards if so.
        exchange_cards = ""
        old_last_line = original_contents[-1] if len(original_contents) > 0 else '\n'
        if old_last_line[-1] != '\n' and old_last_line[0] == 'E' and \
                len(old_last_line) % 2 == 0 and old_last_line[-1] in "p_'<=0":
            exchange_cards = punishment_to_reveal[deck.pop()] + \
                    punishment_to_reveal[deck.pop()]

        cards = exchange_cards + ''.join(
                    punishment_to_reveal[card] for card in current_player.cards)
        args = current_player.command + [
            outfilename,
            str(opponent.coins),
            str(current_player.coins),
            cards
        ] + legal_actions
        print ' '.join(args)
        output = ""
        os.chdir(current_player.name)
        try:
            output = subprocess.check_output(args)
        # Competitors that fail to execute must forfeit
        except subprocess.CalledProcessError:
            print current_player.name, "forfeits by non-zero exit status"
            return opponent
        finally:
            os.chdir('..')

        new_contents = []
        new_contents_joined = ""
        with open(outfilename, 'r') as outfile:
            new_contents = outfile.readlines()
            new_contents_joined = ''.join(new_contents)
        if original_contents_joined != new_contents_joined[:-2] and \
                original_contents_joined != new_contents_joined[:-1]:
            print current_player.name, "forfeits by modifying the file"
            print "old:", original_contents
            print "new:", new_contents
            return opponent
        new_last_line = new_contents[-1]
        the_move_made = ""
        for action in legal_actions:
            if new_last_line.endswith(action):
                the_move_made = action
                break
        # Competitors that make an illegal move must forfeit
        if not the_move_made:
            print current_player.name, "forfeits with an illegal move,",\
                    "last line: %r" % new_last_line
            print opponent.name, "wins!"
            return opponent
        print current_player.name, "played %r" % the_move_made
        # Side effects of moves.
        #
        # Income, give the current player a coin.
        if the_move_made == "I\n":
            print current_player.name, "received 1 coin of income"
            current_player.coins += 1
        # The program surrendered a card on its turn; take it away. 
        elif len(the_move_made) == 2:
            print current_player.name, "lost a card from being challenged"
            current_player.cards.remove(the_move_made[0])
            # Coins are not returned from a successful Contessa block
            if new_last_line[-3] == '!':
                print current_player.name, "lost 3 coins from a Contessa block"
                current_player.coins -= 3
        # The program surrendered a card when it was not its turn.
        elif the_move_made in "_'<=0":
            print current_player.name, "gave up a", the_move_made
            current_player.cards.remove(the_move_made)
            if new_last_line[0] == 'C':
                opponent.coins -= 7
            elif new_last_line[0] == 'A':
                opponent.coins -= 3
            # Did the program unsuccessfully challenge an Assassination
            # (e.g. Aq^0\n)
            # or get caught falsely blocking with a Contessa
            # (e.g. Asq0\n)?
            # If yes, it loses right away.
            if new_last_line[0] == 'A' and new_last_line[1] in 'qs' and \
                    len(new_last_line) == 4:
                print current_player.name, "lost both cards in the same turn."
                print opponent.name, "wins!"
                return opponent
        elif the_move_made == 'S':
            print current_player.name, "attempted Steal"
        elif the_move_made == 'T':
            print current_player.name, "attempted Tax"
        elif the_move_made == 'A':
            print current_player.name, "attempted Assassinate"
        elif the_move_made == 'C':
            print current_player.name, "launched a Coup"
        elif the_move_made == 'F':
            print current_player.name, "attempted Foreign Aid"
        elif the_move_made == 'E':
            print current_player.name, "attempted Exchange"
        elif the_move_made == 'q':
            print current_player.name, "challenged"
        elif the_move_made == 'p':
            print current_player.name, "passed"
        elif the_move_made == 'a':
            print current_player.name, "blocked with an Ambassador"
        elif the_move_made == 'c':
            print current_player.name, "blocked with a Captain"
        elif the_move_made == 's':
            print current_player.name, "blocked with a Contessa"
        elif the_move_made == 'd':
            print current_player.name, "blocked with a Duke"
        # The program revealed a card from an opponent's unsuccessful challenge.
        # Give it a new card.
        # Special case: a program whose Exchange is unsuccessfully challenged
        # may keep the Ambassador it revealed in the Exchange, so give a new
        # card for a revealed Ambassador only if it was used to block a Steal.
        elif the_move_made in '^*!$' or (the_move_made == '~' and
                new_last_line[0] == 'S'):
            p = reveal_to_punishment[the_move_made]
            current_player.cards.remove(p)
            current_player.cards.append(deck.pop())
            deck.append(p)
            random.shuffle(deck)
            print current_player.name, "did have a", the_move_made
        # The program ended its turn. We must examine the rest of the line to
        # determine the side effects.
        elif the_move_made == '\n':
            potential_winner = determine_turn_effects(
                    new_last_line, output.strip(), cards, current_player,
                    opponent)
            if potential_winner:
                print potential_winner.name,\
                        "wins because their opponent made an illegal exchange!"
                return potential_winner

        # One player has lost all their cards. Victory for the opponent!
        if current_player.cards == []:
            print opponent.name, "wins by eliminating both opponent cards!"
            return opponent

        current_player_index += 1
        current_player_index %= 2
    return None

competitors = []
competitors.append(Player("Challenger", ["./challenger"]))
competitors.append(Player("Random", ["./random"]))
# ...More competitors here

for i in range(10):
    print "-- Round", i
    j = 0
    for pairing in itertools.permutations(competitors, 2):
        player1, player2 = pairing
        print '--- Game', j, ':', player1.name, 'vs.', player2.name
        winner = play_game(player1, player2, i, j)
        if not winner:
            j += 1
            continue
        winner.score += 1
        player1.coins = 1
        player1.cards = ""
        player2.coins = 1
        player2.cards = ""
        deck = ['_', "'", '<', '=', '0'] * 3
        random.shuffle(deck)
        j += 1

competitors.sort(reverse=True, key=lambda player: player.score)

for player in competitors:
    print '%5d %s' % (player.score, player.name)

Miscellaneous

One program can not have code specific for another program, and programs can not help each other. (You may have multiple programs, but they can't interact with each other in any way.)

If your program loses both its cards in the same turn, it need only write one. The Arbiter will detect that it has been eliminated.

It is possible and encouraged, but not required, for programs to examine the game's history in the file. By doing so they can determine what cards their opponent has claimed to have and catch them in a lie.

In the real game of Coup, you can challenge an action and then attempt to block it in the same turn. I could not make the specification work if I allowed that, so you may either challenge or block a given action, but not both.

My apologies to @PeterTaylor, who on the previous time I posted this suggested I post it to the sandbox and rework the protocol to pipe output back and forth in STDOUT/STDIN. I tried so, so hard to make that work, spending a full day on it (when I'd already spent a full day writing the original challenge). But Exchanges proved very complicated to implement that way, plus it would have increased the complexity of submissions by requiring them to keep track of their own coin count. So I have posted the challenge more or less as it was originally.

Answer 1

Calculator

Plans out his winning series of moves, and challenges anything that would prevent him from winning.

from __future__ import division
import sys
import random
import operator

_, filename, othercoins, mycoins, mycards = sys.argv[:5]
legalActions = sys.argv[5:]

actions_dict = {'E': '_', 'T': '0', 'A': "'", 'S': '<', 'd': '0', 'a': '_', 'c': '<', 's': '='}
punishment_to_reveal = {'_': '~', "'": '^', '<': '*', '=': '!', '0': '$'}
reveal_to_punishment = {punishment_to_reveal[k]: k for k in punishment_to_reveal}

obviousActions = ['~', '^', '*', '!', '$']
lossActions = ['_', "'", '<', '=', '0']

statefilename = './state.txt'
flags = set()
# Flags:
# 1 We went first
# $ Attacking with Duke
# * Attacking with Captain
# ^ Attacking with Assassin
# d Opponent used Duke
# c Opponent used Captain
# A Opponent used Assassin
# F Opponent used Foreign Aid

with open(statefilename, "a+") as statefile:
    statefile.seek(0)
    if statefile.readline().strip() == filename:
        flags = set(statefile.readline().strip())

with open(filename, "r+") as history:
    line = "\n"
    turn = 0
    oppcardcount = 4 - len(mycards)
    for a in history:
        line = a
        turn += 1
        if [c for c in line if c in lossActions]:
            oppcardcount -= 1
    else:
        flags.add("1")

    mycoins = int(mycoins)
    othercoins = int(othercoins)
    mycardcount = len(mycards)

    if line == 'T':
        othercoins += 3
        flags.add('d')
    elif line == 'S':
        othercoins += (2 if mycoins > 2 else mycoins)
        mycoins -= (2 if mycoins > 2 else mycoins)
        flags.add('c')
    elif line == 'A':
        othercoins -= 3
        mycardcount -= 1
        flags.add('A')
    elif line == 'F':
        flags.add('F')
    elif line == 'I\n':
        # If opponent is backing down, they're not so scary anymore
        flags.discard('d')
        flags.discard('c')
        flags.discard('F')

    # What's the least aggressive play that still wins?
    iGetStolen = ('c' in flags and not '*' in mycards and not '~' in mycards)
    iGetAssassinated = ('A' in flags and not '!' in mycards)
    incomeTimeToWin = max(0,7*oppcardcount-mycoins)+oppcardcount if not iGetStolen else 1000
    faidTimeToWin = max(0,7*oppcardcount-mycoins+1)//2+oppcardcount if not iGetStolen else 1000
    dukeTimeToWin = max(0,7*oppcardcount+(2*(oppcardcount-mycardcount) if iGetStolen else 0)-mycoins+2)//(3 if not iGetStolen else 1)+oppcardcount
    assassinTimeToWin = max(0,3*oppcardcount-mycoins)+oppcardcount if not iGetStolen else oppcardcount if mycoins >= 5*oppcardcount-2 else 1000
    captainTimeToWin = max(0,7*oppcardcount-mycoins+1)//2+oppcardcount
    faidAssassinTimeToWin = max(0,3*oppcardcount-mycoins+1)//2+oppcardcount if not iGetStolen else 1000
    dukeAssassinTimeToWin = max(0,3*oppcardcount+(2*(oppcardcount-mycardcount) if iGetStolen else 0)-mycoins+2)//(3 if not iGetStolen else 1)+oppcardcount
    captainAssassinTimeToWin = max(0,3*oppcardcount-mycoins+1)//2+oppcardcount
    opponentMoneySpeed = (2 if iGetStolen else 3 if 'd' in flags else 2 if 'F' in flags and not '$' in mycards else 1)
    opponentTimeToWin = max(0,(3 if iGetAssassinated else 7)*mycardcount-othercoins+opponentMoneySpeed-1)//opponentMoneySpeed+mycardcount
    opponentTimeToWinCaptained = max(0,(3 if iGetAssassinated else 7)*mycardcount+2*(mycardcount-oppcardcount)-(othercoins-2 if othercoins>2 else 0)+opponentMoneySpeed-3)//(opponentMoneySpeed-2)+mycardcount if opponentMoneySpeed > 2 else 1000

    def pickCardToLose():
        favoriteCards = []
        if dukeTimeToWin < opponentTimeToWin and '$' in mycards:
            favoriteCards = ['$', '!', '*', '~', '^']
        elif dukeAssassinTimeToWin < opponentTimeToWin and ('$' in mycards or '$' in flags) and '^' in mycards:
            favoriteCards = ['^', '$', '!', '*', '~']
        elif assassinTimeToWin < opponentTimeToWin and '^' in mycards:
            favoriteCards = ['^', '!', '*', '~', '$']
        elif captainTimeToWin < opponentTimeToWinCaptained and '*' in mycards:
            favoriteCards = ['*', '!', '$', '^', '~']
        elif faidTimeToWin < opponentTimeToWin and '^' in mycards and not 'd' in flags:
            favoriteCards = ['!', '*', '~', '$', '^']
        elif faidAssassinTimeToWin < opponentTimeToWin and '^' in mycards and not 'd' in flags:
            favoriteCards = ['^', '!', '*', '~', '$']
        elif captainAssassinTimeToWin < opponentTimeToWinCaptained and '*' in mycards and '^' in mycards:
            favoriteCards = ['^', '*', '!', '$', '~']
        else:
            favoriteCards = ['!', '*', '~', '$', '^']
        # Losing a card.  Decide which is most valuable.
        for k in favoriteCards:
            if k in mycards:
                cardToLose = k
        return reveal_to_punishment[cardToLose]

    action = legalActions[0]
    if line == "\n":
        # First turn behavior
        if '$' in mycards and 'T' in legalActions:
            action = 'T'
            flags.add('$')
        elif '*' in mycards and 'S' in legalActions:
            action = 'S'
            flags.add('*')
        elif '^' in mycards and 'I\n' in legalActions:
            action = 'I\n'
            flags.add('^')
        elif '~' in mycards and 'E' in legalActions:
            action = 'E'
        elif 'T' in legalActions:
            # Contessa/Contessa?  Need to lie.
            action = 'T'
            flags.add('$')
    elif set(obviousActions).intersection(legalActions):
        # Always take these actions if possible
        for a in set(obviousActions).intersection(legalActions):
            action = a
        # This might change our strategy
        flags.discard(action)
    elif '$' in mycards and 'd' in legalActions:
        action = 'd'
    elif '~' in mycards and 'a' in legalActions:
        action = 'a'
    elif '*' in mycards and 'c' in legalActions:
        action = 'c'
    elif '!' in mycards and 's' in legalActions:
        action = 's'
    elif 'q' in legalActions and line[-1] in 'dacs':
        # We're committed at this point
        action = 'q'
    elif 'q' in legalActions and '*' in flags and line[-1] in 'SE':
        # Don't allow these when using a steal strategy
        action = 'q'
    elif 'q' in legalActions and turn == 1:
        if line == 'T':
            if mycards == '$$' or mycards == '^^' or mycards == '!!':
                action = 'q'
            else:
                action = 'p'
                flags.add('d')
        elif line == 'S':
            if '$' in mycards and '^' in mycards:
                action = 'p'
                flags.add('c')
            else:
                action = 'q'
        elif line == 'E':
            action = 'p'
    elif line == 'A' and len(mycards) > 1:
        # Don't challenge the first assasination.  We'll get 'em later.
        action = pickCardToLose()
        flags.add('A')
    elif line == 'A':
        # Can't let this pass
        action = 'q'
    elif line == 'C':
        # Taking damage
        action = pickCardToLose()
    elif len(line) == 2 and line[1] == 'q':
        # My base action was successfully challenged
        action = pickCardToLose()+"\n"
        # Also stop claiming what we were challenged for
        if line == "Tq":
            flags.discard('$')
        elif line == "Sq":
            flags.discard('*')
        elif line == "Aq":
            flags.discard('^')
    elif len(line) == 3 and line[1] == 'q':
        # I failed challenging a base action
        action = pickCardToLose()
    elif len(line) == 3 and line[2] == 'q':
        # My block was successfully challenged
        action = pickCardToLose()
    elif len(line) == 4 and line[2] == 'q':
        # I failed challenging a block
        action = pickCardToLose()+"\n"
    else:
        if 'p' in legalActions:
            # Default to pass if no other action is chosen
            action = 'p'

        if dukeTimeToWin <= opponentTimeToWin and ('$' in mycards or '$' in flags):
            if 'C' in legalActions:
                action = 'C'
            elif 'T' in legalActions:
                action = 'T'
        elif incomeTimeToWin <= opponentTimeToWin:
            if 'C' in legalActions:
                action = 'C'
            elif 'I\n' in legalActions:
                action = "I\n"
        elif dukeAssassinTimeToWin <= opponentTimeToWin and ('$' in mycards or '$' in flags) and '^' in mycards and mycardcount > 1:
            if 3*oppcardcount <= mycoins - (2*(oppcardcount-1) if iGetStolen else 0) and 'A' in legalActions:
                action = 'A'
            elif 'T' in legalActions:
                action = 'T'
            flags.add('^');
        elif assassinTimeToWin <= opponentTimeToWin and '^' in mycards:
            if 'A' in legalActions:
                action = 'A'
            elif 'I\n' in legalActions:
                action = 'I\n'
            flags.add('^');
        elif captainTimeToWin <= opponentTimeToWinCaptained and '*' in mycards:
            if 'C' in legalActions:
                action = 'C'
            elif 'S' in legalActions:
                action = 'S'
            elif 'I\n' in legalActions:
                action = 'I\n'
            flags.add('*');
        elif faidTimeToWin <= opponentTimeToWin and not 'd' in flags:
            if 'C' in legalActions:
                action = 'C'
            elif 'F' in legalActions:
                action = 'F'
        elif faidAssassinTimeToWin <= opponentTimeToWin and '^' in mycards and not 'd' in flags:
            if 'A' in legalActions:
                action = 'A'
            elif 'F' in legalActions:
                action = 'F'
            flags.add('^');
        elif captainAssassinTimeToWin <= opponentTimeToWinCaptained and '*' in mycards and '^' in mycards:
            if 'A' in legalActions:
                action = 'A'
            elif 'S' in legalActions:
                action = 'S'
            flags.add('^');
            flags.add('*');
        elif 'q' in legalActions:
            action = 'q'
        # No winning strategy.  Find something useful to do anyway.
        elif 'C' in legalActions and not '^' in flags:
            action = 'C'
        elif 'S' in legalActions and '*' in flags:
            action = 'S'
        elif 'A' in legalActions and '^' in flags:
            action = 'A'
        elif 'E' in legalActions and '~' in mycards and dukeAssassinTimeToWin < opponentTimeToWin:
            action = 'E'
        elif 'F' in legalActions and not 'd' in flags:
            action = 'F'
        elif 'T' in legalActions:
            action = 'T'
            flags.add('$');
    if action == 'q':
        if line == 'T' or line == 'Fd':
            flags.discard('d')
        elif line == 'S' or line == 'Sc':
            flags.discard('c')
        elif line == 'A':
            flags.discard('A')
    history.write(action)

if len(mycards) > 2:
    favoriteCards = []
    if dukeTimeToWin < opponentTimeToWin and '$' in mycards:
        favoriteCards = ['$', '!', '*', '~', '^']
    elif dukeAssassinTimeToWin < opponentTimeToWin and ('$' in mycards or '$' in flags) and '^' in mycards:
        favoriteCards = ['^', '$', '!', '*', '~']
    elif assassinTimeToWin < opponentTimeToWin and '^' in mycards:
        favoriteCards = ['^', '!', '*', '~', '$']
    elif captainTimeToWin < opponentTimeToWinCaptained and '*' in mycards:
        favoriteCards = ['*', '!', '$', '^', '~']
    elif faidTimeToWin < opponentTimeToWin and '^' in mycards and not 'd' in flags:
        favoriteCards = ['!', '*', '~', '$', '^']
    elif faidAssassinTimeToWin < opponentTimeToWin and '^' in mycards and not 'd' in flags:
        favoriteCards = ['^', '!', '*', '~', '$']
    elif captainAssassinTimeToWin < opponentTimeToWinCaptained and '*' in mycards and '^' in mycards:
        favoriteCards = ['^', '*', '!', '$', '~']
    else:
        favoriteCards = ['!', '*', '~', '$', '^']
    # Losing two cards.  Decide which is most valuable.
    possibleCards = [k for k in favoriteCards if k in mycards]
    if len(possibleCards) < len(mycards) - 2:
        possibleCards = list(mycards)
        random.shuffle(possibleCards)
    mycards = ''.join(possibleCards[:(len(mycards)-2)])
    print mycards

with open(statefilename, "w") as statefile:
    statefile.write(filename+"\n")
    statefile.write(''.join(list(flags))+"\n")

Turncoat

Tells the truth at first, but starts lying when it stops being challanged. Also has some solver-behavior. (An approximation of how I behave when playing this game with humans)

import sys
import random

_, filename, othercoins, mycoins, mycards = sys.argv[:5]
legalActions = sys.argv[5:]

actions_dict = {'E': '_', 'T': '0', 'A': "'", 'S': '<', 'd': '0', 'a': '_', 'c': '<', 's': '='}
punishment_to_reveal = {'_': '~', "'": '^', '<': '*', '=': '!', '0': '$'}
reveal_to_punishment = {punishment_to_reveal[k]: k for k in punishment_to_reveal}

obviousActions = ['C', '~', '^', '*', '!', '$']
lossActions = ['_', "'", '<', '=' '0']

statefilename = './state.txt'
myclaims = set()
otherclaims = set()
mycaughtlies = set()
othercaughtlies = set()
flags = set()
# Flags:
# * Opponent had a chance to challenge us just now
# & Opponent has stopped wildly challenging everything
# E We have exchanged at least once
# S Opponent did not block a steal.  Go for the jugular!
# _ Opponent has lost a card

with open(statefilename, "a+") as statefile:
    statefile.seek(0)
    if statefile.readline().strip() == filename:
        myclaims = set(statefile.readline().strip())
        otherclaims = set(statefile.readline().strip())
        mycaughtlies = set(statefile.readline().strip())
        othercaughtlies = set(statefile.readline().strip())
        flags = set(statefile.readline().strip())

def getFavoriteCards():
    favoriteCards = []
    if '*' in otherclaims:
        favoriteCards.append('~')
    elif not '~' in otherclaims:
        favoriteCards.append('*')
    if len(otherclaims) > (0 if '_' in flags else 1) and mycoins > 1 and not '!' in otherclaims:
        favoriteCards.append('^')
    favoriteCards.append('!')
    favoriteCards.append('$')
    if not '~' in favoriteCards:
        favoriteCards.append('~')
    return favoriteCards

def pickCardToLose():
    # Losing a card.  Decide which is most valuable.
    favoriteCards = getFavoriteCards()
    cardToLose = ''
    for k in favoriteCards:
        if k in mycards:
            cardToLose = k
    for k in mycards:
        if not k in favoriteCards:
            cardToLose = k
    return reveal_to_punishment[cardToLose]

with open(filename, "r+") as history:
    line = "\n"
    for a in history:
        line = a
    if 'q' in legalActions:
        otherclaims.add(punishment_to_reveal[actions_dict[line[-1]]])
    if len(line) > 2 and line.endswith('\n') and line[-2] in lossActions:
        otherclaims.discard(punishment_to_reveal[line[-2]])
        flags.add('_')
    if len(line) > 2 and line.endswith('\n') and (line.startswith('Ep') or line.startswith('Eq~')):
        othercaughtlies = set()
    if '*' in flags:
        flags.discard('*')
        if line[-1] not in 'qdacs':
            flags.add('&')
            if line[-2] == 'F':
                othercaughtlies.add('$')
            if line[-2] == 'S':
                othercaughtlies.add('*')
                othercaughtlies.add('~')
            if line[-2] == 'A':
                othercaughtlies.add('!')
    action = legalActions[0]
    if set(obviousActions).intersection(legalActions):
        # Always take these actions if possible
        for a in set(obviousActions).intersection(legalActions):
            action = a
        if action in reveal_to_punishment:
            myclaims.discard(action)
    elif '&' in flags:
        preferredActions = []
        mysafecards = myclaims.union(mycards)

        # Calculate the financial situation
        mygain = 0
        oppgain = 0
        if '*' in mysafecards and not '*' in otherclaims and not '~' in otherclaims:
            mygain += 2
            oppgain -= 2
        elif '$' in mysafecards:
            mygain += 3
        elif not '$' in otherclaims:
            mygain += 1 # This script doesn't use foreign aid
        else:
            mygain += 1
        if '*' in otherclaims and not '*' in mysafecards and not '~' in mysafecards:
            oppgain += 2
            mygain -= 2
        elif '$' in mysafecards:
            oppgain += 3
        elif not '$' in otherclaims:
            oppgain += 2
        else:
            oppgain += 1
        mydist = 7 - int(mycoins)
        oppdist = 7 - int(othercoins)
        if '^' in mysafecards and len(otherclaims) > (0 if '_' in flags else 1) and not '!' in otherclaims:
            mydist -= 4
        if '^' in otherclaims and not '!' in mysafecards:
            oppdist -= 4
        if mydist > 0 and (oppdist <= 0 or mygain <= 0 or (oppgain > 0 and ((oppdist+oppgain-1) // oppgain) < ((mydist+mygain-1) // mygain))):
            # Not winning.  Do something desperate.
            timeToLive = ((oppdist+oppgain-1) // oppgain) if oppdist > 0 else 0
            favoriteCards = getFavoriteCards()
            if timeToLive < len(otherclaims):
                preferredActions.append('q')
            if (timeToLive or len(mycards) > 1) and favoriteCards[0] not in mysafecards:
                preferredActions.append('E')
            elif mycoins >= 3 and random.randint(0,2):
                preferredActions.append('A')
            else:
                preferredActions.append('S')

        preferredActions.append('s')
        if 'a' in legalActions and ('~' in mycards or '*' in mycards) and not 's' in flags:
            # Allow the first steal, as bait
            preferredActions.append('p')
            flags.add('s')
            if '~' in mycards:
                flags.discard('E')
        if '$' in mysafecards:
            preferredActions.append('d')
        if '~' in mysafecards:
            preferredActions.append('a')
        elif '*' in mysafecards:
            preferredActions.append('c')
        else:
            preferredActions.append('c' if random.randint(0,1) else 'a')
        if not 'E' in flags:
            preferredActions.append('E')
        if not ('~' in otherclaims or '*' in otherclaims):
            preferredActions.append('S')
        if len(otherclaims) > (0 if '_' in flags else 1) and ('^' in mycards or not '_' in flags) and not '!' in otherclaims:
            preferredActions.append('A')
        preferredActions.append('T')
        if line[-1] in actions_dict and punishment_to_reveal[actions_dict[line[-1]]] in othercaughtlies:
            preferredActions.append('q')
        preferredActions += ['p', '\n']
        if len(myclaims) < len(mycards):
            # Slip a lie in before admitting all cards in hand
            preferredActions = [a for a in preferredActions
                if not a in actions_dict
                or not punishment_to_reveal[actions_dict[a]] in mysafecards]
        else:
            preferredActions = [a for a in preferredActions
                if not a in actions_dict
                or punishment_to_reveal[actions_dict[a]] in mycards
                or not punishment_to_reveal[actions_dict[a]] in mycaughtlies]
        preferredActions = [a for a in preferredActions if a in legalActions]
        if preferredActions:
            action = preferredActions[0]
        else:
            loss = pickCardToLose()
            if loss in legalActions:
                action = loss
            elif loss+"\n" in legalActions:
                action = loss+"\n"
    else:
        preferredActions = []
        if not ('~' in otherclaims or '*' in otherclaims):
            preferredActions.append('S')
        preferredActions += ['T', 'E', 'd', 'a', 'c', 's', 'p', '\n']
        if not '!' in otherclaims:
            preferredActions.append('A')
        preferredActions = [a for a in preferredActions if a in legalActions]
        # Filter out lies, provided that doesn't filter out everything
        preferredActions = [a for a in preferredActions
            if not a in actions_dict
            or punishment_to_reveal[actions_dict[a]] in mycards
        ] or [a for a in preferredActions
            if not a in actions_dict
            or not punishment_to_reveal[actions_dict[a]] in mycaughtlies
        ]
        if preferredActions:
            action = preferredActions[0]
        else:
            loss = pickCardToLose()
            if loss in legalActions:
                action = loss
            elif loss+"\n" in legalActions:
                action = loss+"\n"
        if 'a' in legalActions:
            if action not in 'acq':
                # If vulnerable to stealing, don't admit it!
                action = random.choice('acq')
            elif not 's' in flags:
                # Allow the first steal, as bait
                action = 'p'
                flags.add('s')
                if '~' in mycards:
                    flags.discard('E')
    if action.strip("\n") in lossActions:
        myclaims.discard(punishment_to_reveal[action.strip("\n")])
        if line[-1] == 'q':
            # Also stop claiming what we were challenged for
            myclaims.discard(punishment_to_reveal[actions_dict[line[-2]]])
            mycaughtlies.add(punishment_to_reveal[actions_dict[line[-2]]])
    if action == 'q':
        # We challenged it.  One way or another, they will not have this card later.
        otherclaims.discard(punishment_to_reveal[actions_dict[line[-1]]])
        othercaughtlies.add(punishment_to_reveal[actions_dict[line[-1]]])
    if action in actions_dict:
        myclaims.add(punishment_to_reveal[actions_dict[action]])
        flags.add('*')
    history.write(action)

if len(mycards) > 2:
    flags.add('E')
    mycaughtlies = set()
    # Losing two cards.  Decide which is most valuable.
    favoriteCards = getFavoriteCards()
    # After an exchange, we can claim what we like.  Throw in some lying for more flexibility.
    myclaims = set()
    possibleCards = [k for k in favoriteCards if k in mycards]
    if random.randint(1,len(possibleCards)) > len(mycards) - 2:
        myclaims.add(possibleCards[0])
        possibleCards = possibleCards[1:]
    if len(possibleCards) < len(mycards) - 2:
        possibleCards = list(mycards)
        random.shuffle(possibleCards)
    mycards = ''.join(possibleCards[:(len(mycards)-2)])
    print mycards

with open(statefilename, "w") as statefile:
    statefile.write(filename+"\n")
    statefile.write(''.join(list(myclaims))+"\n")
    statefile.write(''.join(list(otherclaims))+"\n")
    statefile.write(''.join(list(mycaughtlies))+"\n")
    statefile.write(''.join(list(othercaughtlies))+"\n")
    statefile.write(''.join(list(flags))+"\n")

Bandit

Tries to get rid of the opponent's Ambassadors and Captains, and win by stealing.

import sys
import random

_, filename, othercoins, mycoins, mycards = sys.argv[:5]
legalActions = sys.argv[5:]

actions_dict = {'E': '_', 'T': '0', 'A': "'", 'S': '<', 'd': '0', 'a': '_', 'c': '<', 's': '='}
punishment_to_reveal = {'_': '~', "'": '^', '<': '*', '=': '!', '0': '$'}
reveal_to_punishment = {punishment_to_reveal[k]: k for k in punishment_to_reveal}

obviousActions = ['C', '~', '^', '*', '!', '$']
lossActions = ['_', "'", '<', '=' '0']

def getFavoriteCards():
    return ['*', '!', '~', '$', '^']

def pickCardToLose():
    # Losing a card.  Decide which is most valuable.
    favoriteCards = getFavoriteCards()
    cardToLose = ''
    for k in favoriteCards:
        if k in mycards:
            cardToLose = k
    for k in mycards:
        if not k in favoriteCards:
            cardToLose = k
    return reveal_to_punishment[cardToLose]

with open(filename, "r+") as history:
    line = "\n"
    turn = 0
    for a in history:
        line = a
        turn += 1
    action = legalActions[0]
    if set(obviousActions).intersection(legalActions):
        # Always take these actions if possible
        for a in set(obviousActions).intersection(legalActions):
            action = a
    elif 'p' in legalActions and turn == 1 and line == "E":
        # Let this pass... once
        action = 'p'
    elif 'q' in legalActions and line[-1] in 'SEac':
        # These get in the way of stealing, get rid of them even if it costs us a card
        action = 'q'
    elif 'E' in legalActions and '~' in mycards and '*' not in mycards:
        action = 'E'
    elif 'S' in legalActions:
        action = 'S'
    elif 's' in legalActions:
        if '!' in mycards:
            action = 's'
        elif len(mycards) == 1:
            action = random.choice('sq')
        else:
            action = pickCardToLose()
    elif 'p' in legalActions:
        action = 'p'
    elif line == 'A' or line == 'C':
        # Taking damage
        action = pickCardToLose()
    elif len(line) == 2 and line[1] == 'q':
        # My base action was successfully challenged
        action = pickCardToLose()+"\n"
    elif len(line) == 3 and line[1] == 'q':
        # I failed challenging a base action
        action = pickCardToLose()
    elif len(line) == 3 and line[2] == 'q':
        # My block was successfully challenged
        action = pickCardToLose()
    elif len(line) == 4 and line[2] == 'q':
        # I failed challenging a block
        action = pickCardToLose()+"\n"
    history.write(action)

if len(mycards) > 2:
    # Losing two cards.  Decide which is most valuable.
    favoriteCards = getFavoriteCards()
    possibleCards = [k for k in favoriteCards if k in mycards]
    if mycards.count('*') > 1:
        # Hooray captains!
        possibleCards = ['*'] + possibleCards
    if len(possibleCards) < len(mycards) - 2:
        possibleCards = list(mycards)
        random.shuffle(possibleCards)
    mycards = ''.join(possibleCards[:(len(mycards)-2)])
    print mycards

Bloody Murder

A counterpart to Bandit, this one goes all-in on a Duke+Assassin strategy.

import sys
import random

_, filename, othercoins, mycoins, mycards = sys.argv[:5]
legalActions = sys.argv[5:]

actions_dict = {'E': '_', 'T': '0', 'A': "'", 'S': '<', 'd': '0', 'a': '_', 'c': '<', 's': '='}
punishment_to_reveal = {'_': '~', "'": '^', '<': '*', '=': '!', '0': '$'}
reveal_to_punishment = {punishment_to_reveal[k]: k for k in punishment_to_reveal}

obviousActions = ['C', '~', '^', '*', '!', '$']
lossActions = ['_', "'", '<', '=' '0']

def getFavoriteCards():
    return ['^', '$', '!', '*', '~']

def pickCardToLose():
    # Losing a card.  Decide which is most valuable.
    favoriteCards = getFavoriteCards()
    cardToLose = ''
    for k in favoriteCards:
        if k in mycards:
            cardToLose = k
    for k in mycards:
        if not k in favoriteCards:
            cardToLose = k
    return reveal_to_punishment[cardToLose]

with open(filename, "r+") as history:
    line = "\n"
    stealHappened = 0
    oppcardcount = 4 - len(mycards)
    for a in history:
        line = a
        if line[0] == 'S':
            stealHappened = 1
        if [c for c in line if c in lossActions]:
            oppcardcount -= 1
    action = legalActions[0]
    if set(obviousActions).intersection(legalActions):
        # Always take these actions if possible
        for a in set(obviousActions).intersection(legalActions):
            action = a
    elif 'q' in legalActions and line[-1] in 's':
        # We need this gone
        action = 'q'
    elif 'E' in legalActions and '~' in mycards:
        action = 'E'
    elif 'A' in legalActions and (len(mycards) == 1 or mycoins >= 3*oppcardcount+(2 if stealHappened and oppcardcount>1 else 0)):
        action = 'A'
    elif 'T' in legalActions:
        action = 'T'
    elif 'd' in legalActions:
        action = 'd'
    elif 'c' in legalActions and '*' in mycards:
        action = 'c'
    elif 'a' in legalActions and '~' in mycards:
        action = 'a'
    elif 's' in legalActions:
        if '!' in mycards:
            action = 's'
        elif len(mycards) == 1:
            action = random.choice('sq')
        else:
            action = pickCardToLose()
    elif 'p' in legalActions:
        action = 'p'
    elif line == 'A' or line == 'C':
        # Taking damage
        action = pickCardToLose()
    elif len(line) == 2 and line[1] == 'q':
        # My base action was successfully challenged
        action = pickCardToLose()+"\n"
    elif len(line) == 3 and line[1] == 'q':
        # I failed challenging a base action
        action = pickCardToLose()
    elif len(line) == 3 and line[2] == 'q':
        # My block was successfully challenged
        action = pickCardToLose()
    elif len(line) == 4 and line[2] == 'q':
        # I failed challenging a block
        action = pickCardToLose()+"\n"
    history.write(action)

if len(mycards) > 2:
    # Losing two cards.  Decide which is most valuable.
    favoriteCards = getFavoriteCards()
    possibleCards = [k for k in favoriteCards if k in mycards]
    if mycards.count('^') > 1:
        # Hooray assassins!
        possibleCards = ['^'] + possibleCards
    if len(possibleCards) < len(mycards) - 2:
        possibleCards = list(mycards)
        random.shuffle(possibleCards)
    mycards = ''.join(possibleCards[:(len(mycards)-2)])
    print mycards

Answer 2

Solver

Solver try to remember what cards are played before and what was the previous moves of the opponent.

this is the 2nd version not finished yet (and it is a big mess now)

to make it work on node 10 add competitors.append(Player("Solver", ["node", "--experimental-modules", "./solver.mjs"]))

if node 12 competitors.append(Player("Solver", ["node", "./solver.js"]))

be carefull with the file type

import  fs from 'fs'
import { promisify } from 'util'

const appendFile = promisify(fs.appendFile)
const writeFile = promisify(fs.writeFile)
const readFile = promisify(fs.readFile)

const delay = ms => new Promise(_ => setTimeout(_, ms));

let [filename, othercoins, mycoins, mycards ] = process.argv.slice(2)
othercoins = +othercoins
mycoins = +mycoins

const move = async m => await appendFile(filename, m)
const message = m => process.stdout.write(m)
const endTurn = async _ => await move(`\n`) 

const stateFileName = `./state.json`

const defaultState = {
    inTheDeck: [],
    oponentCards: [],
    oponentMissingTempCard: "",
    oponentMissingCards: [],
    oponentDropedCards: [],
    oponentCardModifier: 0
}

const CardTypes = Object.freeze({
    Ambassador : `Ambassador`,
    Assassin : `Assassin`,
    Captain  : `Captain`,
    Contessa : `Contessa`,
    Duke     : `Duke`,
})

const revealTable = Object.freeze({
    [CardTypes.Ambassador]: `~`,
    [CardTypes.Assassin]: `^`,
    [CardTypes.Captain]: `*`,
    [CardTypes.Contessa]: `!`,
    [CardTypes.Duke]: `$`,
})

const giveUpTable = Object.freeze({
    [CardTypes.Ambassador]: `_`,
    [CardTypes.Assassin]: `'`,
    [CardTypes.Captain]: `<`,
    [CardTypes.Contessa]: `=`,
    [CardTypes.Duke]: `0`,
})

function GetRevealCardChar(cardType) {
    return revealTable[cardType]
}

function GetRevealCardType(char) {
    return Object.keys(revealTable).find(key => revealTable[key] === char)
}

function GetGiveUpCardChar(cardType) {
    return giveUpTable[cardType]
}

function GetGiveUpCardType(char) {
    return Object.keys(giveUpTable).find(key => giveUpTable[key] === char)
}

async function GiveUpCard(cardType, endTurn = false) {
    return await move(
        GetGiveUpCardChar(cardType) + `${endTurn?`\n`:``}`
    );
}

function OponentCanHave(cardType) {
    // it has it
    if (!!~state.oponentCards.indexOf(cardType)) return true

    if (state.oponentCards.length + state.oponentDropedCards.length >= 2) return false

    return true
}


function GiveCard(getOrder = false) {
    // TODO: Tactic
    const giveAwayOrder = [
        CardTypes.Captain,
        CardTypes.Ambassador,
        CardTypes.Contessa,
        CardTypes.Assassin,
        CardTypes.Duke,
    ]

    const tmp =  mycards
        .split('')
        .map(GetRevealCardType)

    let [unique, duplicate] = tmp.reduce(([unique, duplicate], item) => {
        return unique.includes(item) ? 
            [unique, [...duplicate, item]] :
            [[...unique, item], duplicate]
    }
    , [[],[]])

    unique.sort(
        (a, b) => giveAwayOrder.indexOf(a) - giveAwayOrder.indexOf(b));
    duplicate.sort(
        (a, b) => giveAwayOrder.indexOf(a) - giveAwayOrder.indexOf(b))

    const out = [...duplicate, ...unique]

    return getOrder? out: GetGiveUpCardChar(out[0]);
}

const iHaveAmbassador = !!~mycards.indexOf(`~`)
const iHaveAssassin = !!~mycards.indexOf(`^`)
const iHaveCaptain = !!~mycards.indexOf(`*`)
const iHaveContessa = !!~mycards.indexOf(`!`)
const iHaveDuke = !!~mycards.indexOf(`$`)

let state = defaultState

;(async ()=>{
    const data = (await readFile(filename, `utf8`)).replace(/\r/g, ``)

    const isNewGame = data === "" && mycoins === 1 && othercoins === 1

    if (isNewGame) {
        await writeFile(stateFileName, JSON.stringify(state))
    } else {
        state = JSON.parse(await readFile(stateFileName, `utf8`))
    }
    //console.error(state);
    let line = data.split(/\n/g).pop()

    // I am in the exchnage
    if (mycards.length >= 3) {
        const [c1, c2] = GiveCard(true).reverse()

        if (mycards.length === 3) {
            state.inTheDeck.push(c1)
            message(GetRevealCardChar(c1))
        }
        if (mycards.length === 4) {
            state.inTheDeck.push(c1, c2)
            message(`${GetRevealCardChar(c1)}${GetRevealCardChar(c2)}`)
        }
        return await move(`\n`)
    }

    const newTurn = line === ``

    if (newTurn) {
        if (mycoins >= 7) {
            return await move(`C`)
        }

        if (othercoins >= 6) {
            if (iHaveCaptain) 
                return await move(`S`)


            if (mycoins <= 6 && mycards.length <= 1) {
                // TODO: bluff 
            }
        }

        if (
            !iHaveDuke &&
            !iHaveContessa &&
            iHaveAmbassador
        ) {
            return await move(`E`)
        }

        // Assasinate if oponent has no Contessa
        if (
            mycoins >= 3 &&
            iHaveAssassin &&
            !~state.oponentCards.indexOf(CardTypes.Contessa)
        ) {
            return await move(`A`)
        }

        if (iHaveDuke) {

            return await move(`T`)
        }

        return await move(`I\n`)
    }

    // Exchange
    if (line === `Eq`) {
        if (iHaveAmbassador)
            return await move(GetRevealCardChar(CardTypes.Ambassador))

        return await GiveUpCard(GiveCard(true)[0])
    }

    // Tax Challenge
    if(line === `Tq`) {
        if (iHaveDuke)
            return await move(GetRevealCardChar(CardTypes.Duke))

        return await GiveUpCard(GiveCard(true)[0])
    }


    if (line === `Sa`) {
        if (!~state.oponentCards.indexOf(CardTypes.Ambassador)) {
            state.oponentMissingTempCard = CardTypes.Ambassador
            return await move(`q`)
        }
        return await endTurn()
    }

    if (line === `Sc`) {
        if (!~state.oponentCards.indexOf(CardTypes.Captain)) {
            state.oponentMissingTempCard = CardTypes.Captain
            return await move(`q`)
        }
        return await endTurn()
    }

    if (line=== `Saq${GetRevealCardChar(CardTypes.Ambassador)}`) {
        state.oponentMissingTempCard = ``
        state.oponentCards.push(
            CardTypes.Ambassador
        );
        return await GiveUpCard(GiveCard(true)[0], true)
    }

    if (line=== `Scq${GetRevealCardChar(CardTypes.Captain)}`) {
        state.oponentMissingTempCard = ``
        state.oponentCards.push(
            CardTypes.Captain
        );
        return await GiveUpCard(GiveCard(true)[0], true)
    }

    if (line === `Sq`) {
        if (iHaveCaptain)
            return await move(GetRevealCardChar(CardTypes.Captain))

        return await GiveUpCard(GiveCard(true)[0])
    }

    // Assassinate Block and Chalange it
    if (line === `As`) {
        state.oponentMissingTempCard = CardTypes.Contessa
        return await move(`q`)
    }

    // Assasint blocked by Contessa
    if (line === `Asq${GetRevealCardChar(CardTypes.Contessa)}`) {
        state.oponentMissingTempCard = ``
        state.oponentCards.push(
            CardTypes.Contessa
        )
        // Assassin useless here lets give it up
        return await GiveUpCard(CardTypes.Assassin, true)
    }

    // Assassinate challenge
    if (line === `Aq`) {
        if (iHaveAssassin)
            return await move(GetRevealCardChar(CardTypes.Assassin))

        return await GiveUpCard(GiveCard(true)[0])
    }


    // Defense Moves
    if (line === `C`) {
        return await GiveUpCard(GiveCard(true)[0])
    }


    if (line === `A`) {
        if (iHaveContessa)
            return await move(`s`)


        if (!!~state.oponentCards.indexOf(CardTypes.Assassin)) {
            // If oponent has an Assasin card lets bluff
            return await move(`s`)
        } else {
            state.oponentMissingTempCard = CardTypes.Assassin
            return await move(`q`)
        }

    }

    if (line === `Aq${GetRevealCardChar(CardTypes.Assassin)}`) {
        state.oponentMissingTempCard = ``
        state.oponentCards.push(
            CardTypes.Assassin
        );
        return await GiveUpCard(GiveCard(true)[0], true)
    }

    if (line === `Asq`) {
        if (iHaveContessa)
            return await move(GetRevealCardChar(CardTypes.Contessa))

        return await GiveUpCard(GiveCard(true)[0])
    }

    if (line === `S`) {
        if (iHaveAmbassador)
            return await move(`a`)

        if (iHaveCaptain)
            return await move(`c`)

        return await move(`p`)
    }

    if (line === `Saq`) {
        if (iHaveAmbassador)
            return await move(GetRevealCardChar(CardTypes.Ambassador))

        return await GiveUpCard(GiveCard(true)[0])
    }

    if (line === `Scq`) {
        if (iHaveCaptain)
            return await move(GetRevealCardChar(CardTypes.Captain))

        return await GiveUpCard(GiveCard(true)[0])
    }

    if (line === `F`) {
        if (iHaveDuke)
            return await move(`d`)

        return await move(`p`)
    }

    if (line === `Fdq`) {
        if (iHaveDuke)
            return await move(GetRevealCardChar(CardTypes.Duke))

        return await GiveUpCard(GiveCard(true)[0])
    }

    if (line === `E`) {
        if (!OponentCanHave(CardTypes.Ambassador)) {
            return await move(`q`)
        }

        state.oponentCards = []
        state.oponentMissingCards = []
        state.oponentMissingTempCard = ''

        return await move(`p`)
    }


    if (line === `Eq${GetRevealCardChar(CardTypes.Ambassador)}`) {
        console.error(111, `THIS SHOULD NEVER HAPPEN`)
        return await GiveUpCard(GiveCard(true)[0])
    }

    if (line === `T`) {
        if (!OponentCanHave(CardTypes.Duke)) {
            return await move(`q`)
        }
        return await move(`p`)
    }

    if (line === `Tq${GetRevealCardChar(CardTypes.Duke)}`) {
        console.error(111, `THIS SHOULD NEVER HAPPEN`)
        return await GiveUpCard(GiveCard(true)[0])
    }


    // remove oponents drop card from the state
    // can't detect if oponent has the same card twice
    if (!!~Object.values(giveUpTable).indexOf(line.substr(-1))) {
        // Catch the bluff
        if (state.oponentMissingTempCard !== "") {
            state.oponentMissingCards.push(state.oponentMissingTempCard)
            state.oponentMissingTempCard = ""
        }

        // maybe we should asume user doeas not has the same card?

        const cardType = GetGiveUpCardType(line.substr(-1))
        state.oponentCards.filter(c => c !== cardType)
        state.inTheDeck.push(cardType)
        state.oponentDropedCards.push(cardType)
    }

    return await endTurn()

})()
.then(async () => {
    await writeFile(stateFileName, JSON.stringify(state))
})
.catch(console.error.bind(console))


```

Answer 3

Lawyer

The Lawyer makes his way cautiously through the world, never lying, blocking when possible, challenging when not to his immediate detriment. He does not attack except when required by couping, but will take coins as often as possible in order to coup quickly. He is smart enough to sacrifice cards he does not use first, but not smart enough to use them to get rid of them and get new ones.

import sys

_, filename, othercoins, mycoins, mycards = sys.argv[:5]


def give_card():
    if "^" in mycards:
        return "'"
    if "~" in mycards:
        return "_"
    if "!" in mycards:
        return "="
    if "*" in mycards:
        return "<"
    return "0"


with open(filename, "r+") as history:
    line = "\n"
    for a in history:
        print("line:", a)
        line = a
    if line.endswith("\n"):
        if int(mycoins) >= 10:
            history.write("C")
        elif "$" in mycards:
            history.write("T")
        elif "*" in mycards and int(othercoins) > 0:
            history.write("S")
        else:
            history.write("F")
    elif line == "F":
        if "$" in mycards:
             history.write("d")
        else:
             history.write("p")
    elif line == "C":
        history.write(give_card())
    elif line == "E":
        if len(mycards) > 1:
            history.write("q")
        else: 
            history.write("p")
    elif line == "T":
        if len(mycards) > 1:
            history.write("q")
        else: 
            history.write("p")
    elif line == "A":
        if "!" in mycards:
            history.write("s")
        else: 
            history.write(give_card())
    elif line == "S":
        if "~" in mycards:
            history.write("a")
        elif "*" in mycards:
            history.write("c")
        elif len(mycards) > 1:
            history.write("q")
        else:
            history.write("p")
    elif line.endswith("d") and len(mycards) > 1:
        history.write("q")
    elif line.endswith("a") and len(mycards) > 1:
        history.write("q")
    elif line.endswith("c") and len(mycards) > 1:
        history.write("q")
    elif line.endswith("s") and len(mycards) > 1:
        history.write("q")
    elif line.endswith("sq"):
        history.write("!")
    elif line.endswith("aq"):
        history.write("~")
    elif line.endswith("cq"):
        history.write("*")
    elif line.endswith("dq"):
        history.write("$")
    elif line.endswith("Tq"):
        history.write("$")
    elif line.endswith("Sq"):
        history.write("*")
    elif line[-1] in "~^*!$":
        history.write(give_card())
        if line[-3] in "acds":
            history.write("\n")
    else:
        history.write("\n")

There are probably bugs in this program. When you find them, please let me know.

Answer 4

Random

Random doesn't know what to do, so he randomly selects something legal.

package main

import (
    "fmt"
    "math/rand"
    "os"
    "time"
)

func main() {
    rand.Seed(time.Now().UnixNano())
    filename := os.Args[1]
    ourCards := os.Args[4]
    legalActions := os.Args[5:]
    file, _ := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND, 0755)
    defer file.Close()

    file.WriteString(legalActions[rand.Intn(len(legalActions))])
    switch len(ourCards) {
    case 3:
        os.Stdout.Write([]byte{ourCards[rand.Intn(3)]})
    case 4:
        i1 := 0
        i2 := 0
        for ok := true; ok; ok = i1 == i2 {
            i1 = rand.Intn(4)
            i2 = rand.Intn(4)
        }
        keptCards := []byte{ourCards[i1], ourCards[i2]}
        os.Stdout.Write(keptCards)
    }
}

Challenger

Challenger trusts no one in this game of deception. If you do something challengeable, he will challenge you. Otherwise he just takes income every turn and tries to Coup you if he has the coins.

package main

import (
    "bytes"
    "fmt"
    "io/ioutil"
    "os"
    "strconv"
)

var revealToPunishment = map[byte]byte{'~': '_', '^': '\'', '*': '<', '!': '=', '$': '0'}

func main() {
    filename := os.Args[1]
    coinCount := os.Args[3]
    ourCards := os.Args[4]
    file, _ := os.OpenFile(filename, os.O_RDWR, 0755)
    defer file.Close()

    rawBytes, _ := ioutil.ReadAll(file)
    if len(rawBytes) == 0 {
        file.Write([]byte("I\n"))
        return
    }
    lines := bytes.Split(rawBytes, []byte{'\n'})
    switch rawBytes[len(rawBytes)-1] {
    case '\n':
        // Our turn, do we have enough coins for a Coup?
        if c, _ := strconv.Atoi(coinCount); c >= 7 {
            file.Write([]byte{'C'})
            // We don't, so take income.
        } else {
            file.Write([]byte("I\n"))
        }
    // Opponent did something challengeable. We don't believe them for a second.
    // Challenge it.
    case 'E', 'T', 'A', 'S', 'a', 'c', 'd', 's':
        file.Write([]byte{'q'})
    // Opponent Couped us or our challenge failed. Give up a card.
    case 'C':
        file.Write([]byte{revealToPunishment[ourCards[0]]})
    case '~', '*', '^', '!', '$':
        file.Write([]byte{revealToPunishment[ourCards[0]]})
        lastLine := lines[len(lines)-1]
        switch lastLine[len(lastLine)-3] {
        case 'a', 'c', 'd', 's':
            file.WriteString("\n")
        }
    // Our challenge succeeded or we Couped the opponent! End our turn.
    case '_', '\'', '<', '=', '0':
        file.Write([]byte{'\n'})
    default:
        // Opponent took some other action. Let it pass.
        file.Write([]byte{'p'})
    }
}

Compile these programs with go build random.go/challenger.go and run with ./random or ./challenger.

Answer 5

Taxman

The Taxman is here to collect tax. Uses assassin if they have one. Only blocks if they have the card to block. Randomly challenges.

Written in c#, I spent far too long building a class hierarchy for all the different actions that can be taken.

Edit: Now with improved logic like not claiming to have a duke when they've given up a duke after being challenged. Also no longer tries to continually assasinate if the opponent blocks with contessa (and isn't challenged).

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;

internal static class Program
{
    public static void Main(string[] args)
    {
#if DEBUG
        // Can't figure out how to pass newline as a command line arg.
        for (int i = 0; i < args.Length; i++)
        {
            if (args[i] == "I\\n")
                args[i] = "I\n";
        }
#endif
        if (!ProcessArgs(args, out string filename, out int opCoin, out int myCoin, out IEnumerable<Card> cards, out IEnumerable<Output> validOutputs))
        {
            Console.WriteLine("Error with args.");
            return;
        }

        var taxman = new Taxman(filename, opCoin, myCoin, cards, validOutputs);
        taxman.DukeEm();
    }

    private static bool ProcessArgs(string[] args, out string filename, out int opCoin, out int myCoin, out IEnumerable<Card> cards, out IEnumerable<Output> validOutputs)
    {
        if (args.Length < 4)
        {
            throw new InvalidOperationException("Error: Not enough args.");
        }
        bool success = true;

        filename = args[0];
        success &= int.TryParse(args[1], out opCoin) && opCoin >= 0 && opCoin <= 12;
        success &= int.TryParse(args[2], out myCoin) && myCoin >= 0 && myCoin <= 12;

        cards = Card.ParseSymbols(args[3]);

        IEnumerable<char> validOutputArgs = args.Skip(4).Select(outputArg => outputArg.First());
        // Income and Surrenders on our turn include \n, we use chars below so don't include the newline, hence the call to .First().
        // Code below should be smart enough to also write a newline if necessary.

        validOutputs = Output.ParseSymbols(validOutputArgs);
        return success;
    }
}

internal sealed class Taxman
{
    private const string _OustedAsDukeFileName = "MyTotallyCoolStateFile.txt";
    private const string _OppClaimsContessaFileName = "OppClaimsContess.txt";
    private readonly Random _Rand = new Random();
    private readonly List<Card> _GiveUpPreferences = new List<Card> { Card.Duke, Card.Assassin, Card.Ambassador, Card.Contessa, Card.Captain };

    private double BaseProbabilityToChallenge => 0.1d;
    private bool _Written = false;
    private bool _MyTurn;
    private bool? _OustedAsDuke = null;
    private bool? _OppClaimsContessa = null;

    private string FileName { get; }
    private int OppCoin { get; }
    private int MyCoin { get; }
    private IEnumerable<Card> Cards { get; }
    private IEnumerable<Output> ValidOutputs { get; }
    private IEnumerable<Output> GameSoFar { get; }
    private int OppCardCount { get; }
    private int MyCardCount => Cards.Count();

    private int OppScore => (10 * OppCardCount) + OppCoin;
    private int MyScore => (10 * MyCardCount) + MyCoin;

    private bool OustedAsDuke
    {
        get
        {
            if (_OustedAsDuke.HasValue)
            {
                return _OustedAsDuke.Value;
            }
            else
            {
                if (string.IsNullOrWhiteSpace(File.ReadAllText(_OustedAsDukeFileName)))
                {
                    _OustedAsDuke = false;
                    return false;
                }
                else
                {
                    _OustedAsDuke = true;
                    return true;
                }
            }
        }
        set
        {
            File.WriteAllText(_OustedAsDukeFileName, value ? "Ousted" : string.Empty);
            _OustedAsDuke = value;
        }
    }

    private bool OppClaimsContessa
    {
        get
        {
            if (_OppClaimsContessa.HasValue)
            {
                return _OppClaimsContessa.Value;
            }
            else
            {
                if (string.IsNullOrWhiteSpace(File.ReadAllText(_OppClaimsContessaFileName)))
                {
                    _OppClaimsContessa = false;
                    return false;
                }
                else
                {
                    _OppClaimsContessa = true;
                    return true;
                }
            }
        }
        set
        {
            File.WriteAllText(_OppClaimsContessaFileName, value ? "Claimed" : string.Empty);
            _OppClaimsContessa = value;
        }
    }

    public Taxman(string fileName, int oppCoin, int myCoin, IEnumerable<Card> cards, IEnumerable<Output> validOutputs)
    {
        FileName = fileName; OppCoin = oppCoin; MyCoin = myCoin; Cards = cards; ValidOutputs = validOutputs;

        GameSoFar = ReadFile();

        //calculate how many cards the opponent has.
        int giveUps = GameSoFar.Count(output => output is GiveUp);
        int myGiveUps = 2 - MyCardCount;
        var oppGiveUps = giveUps - myGiveUps;
        OppCardCount = 2 - oppGiveUps;
    }

    public void DukeEm()
    {
        if (Cards.Skip(2).Any())
        {
            Exchange();
            Write(Output.EndTurn);
            return;
        }

        var prev = GameSoFar.LastOrDefault() ?? Output.EndTurn;
        if (prev == Output.EndTurn) // Income is I\n so shows up as an EndTurn
        {
            ChooseAction();
        }
        else if (prev == Action.ForeignAid)
        {
            if (!OustedAsDuke)
                Write(Block.Duke);
            else
                Write(Output.Pass);
        }
        else if (prev == Action.Coup)
        {
            GiveUpDecide();
        }
        else if (prev == ChallengeableAction.Exchange || prev == ChallengeableAction.Tax)
        {
            if (ShouldChallenge((ChallengeableAction)prev))
                Write(Output.Challenge);
            else
                Write(Output.Pass);
        }
        else if (prev == ChallengeableAction.Assassinate)
        {
            RespondToAssassinate();
        }
        else if (prev == ChallengeableAction.Steal)
        {
            RespondToSteal();
        }
        else if (prev == Block.Duke || prev == Block.Ambassador || prev == Block.Captain || prev == Block.Contessa)
        {
            Debug.Assert(prev == Block.Contessa, "We should never take an action that a different card would block.");

            if (ShouldChallenge((Block)prev))
                Write(Output.Challenge);
            else
            {
                Write(Output.EndTurn);
                OppClaimsContessa = true;
            }
        }
        else if (prev == Output.Pass)
        {
            Write(Output.EndTurn);
        }
        else if (prev == Output.Challenge)
        {
            var challengedOutput = (IChallengeable)GameSoFar.TakeLast(2).First();
            RespondToChallenge(challengedOutput);
        }
        else if (prev is Card)
        {
            GiveUpDecide();
        }
        else if (prev is GiveUp)
        {
            if (prev == GiveUp.Contessa)
                OppClaimsContessa = false;

            Write(Output.EndTurn);
        }
        else
        {
            Debug.Fail("Should have hit one of the conditions above.");
            WriteRandomValid();
        }
    }

    private void Exchange()
    {
        int handSize = MyCardCount - 2;
        var cardsToKeep = new List<Card>();
        var workingCards = Cards.ToList();

        while (cardsToKeep.Count < handSize)
        {
            if (!cardsToKeep.Contains(Card.Duke) && workingCards.Remove(Card.Duke))
                cardsToKeep.Add(Card.Duke);
            else if (!cardsToKeep.Contains(Card.Assassin) && !OppClaimsContessa && workingCards.Remove(Card.Assassin))
                cardsToKeep.Add(Card.Assassin);
            else if (!cardsToKeep.Contains(Card.Ambassador) && workingCards.Remove(Card.Ambassador))
                cardsToKeep.Add(Card.Ambassador);
            else if (!cardsToKeep.Contains(Card.Contessa) && workingCards.Remove(Card.Contessa))
                cardsToKeep.Add(Card.Contessa);
            else if (!cardsToKeep.Contains(Card.Captain) && workingCards.Remove(Card.Captain))
                cardsToKeep.Add(Card.Captain);
            else
            {
                cardsToKeep.Add(workingCards[0]);
                workingCards.RemoveAt(0);
            }
        }
        var keptCards = new string(cardsToKeep.Select(card => card.Symbol).ToArray());
        Console.WriteLine(keptCards);
    }

    private IEnumerable<Output> ReadFile()
    {
        var text = File.ReadAllText(FileName);

        // Check if we're at the start of the game, 1 character means our opponent went first.
        if (text == null || text.Length <= 1)
        {
            // Do any start up like creating a state file.
            Debug.Assert(MyCardCount == 2 && MyCoin == 1 && OppCoin == 1, "Should always start with 2 cards in hand and have 1 coin each.");
            using (File.Create(_OustedAsDukeFileName))
            using (File.Create(_OppClaimsContessaFileName))
            { ; }
        }

        var lastLine = text.Split('\n').LastOrDefault();
        _MyTurn = lastLine == null || lastLine.Length % 2 == 0;

        return Output.ParseSymbols(text);
    }

    private void ChooseAction()
    {
        if (MyCoin >= 3 && Cards.Contains(Card.Assassin))
        {
            // If we have the coins to assasinate and have the card to assasinate then go for it.
            Write(ChallengeableAction.Assassinate);
        }
        else if (MyCoin >= 7)
        {
            // If we have the coins to coup then go for it.
            Write(Action.Coup);
        }
        else if (Cards.Contains(Card.Ambassador) && !Cards.Contains(Card.Duke))
        {
            // If we don't /actually/ have a duke but we do have ambassador and can exchange into one, then try do that.
            Write(ChallengeableAction.Exchange);
            // TODO if we've exchanged multiple times already perhaps we should try something different?
        }
        else if (!OustedAsDuke)
        {
            // Take tax because We totally always have a duke.
            // Except if we've been previously challenged and shown to not have a duke, in which case exchange to get a new Duke.
            Write(ChallengeableAction.Tax);
        }
        else
        {
            Write(ChallengeableAction.Exchange);
            // Even if we don't find a duke from the exchange we can pretend that we did.
            OustedAsDuke = false;
        }
    }

    private void RespondToAssassinate()
    {
        if (Cards.Contains(Card.Contessa))
            Write(Block.Contessa);
        else if (MyCardCount <= 1)
        {
            // We will lose if we don't challenge or block.
            if (ShouldRandomChallenge(0.5d))
                Write(Output.Challenge);
            else
                Write(Block.Contessa);
        }
        else if (ShouldChallenge(ChallengeableAction.Assassinate))
            Write(Output.Challenge);
        else
            GiveUpDecide();
    }

    private void RespondToSteal()
    {
        // prefer to block with ambassador before captain.
        if (Cards.Contains(Card.Ambassador))
            Write(Block.Ambassador);
        else if (Cards.Contains(Card.Captain))
            Write(Block.Captain);
        else if (ShouldChallenge(ChallengeableAction.Steal))
            Write(Output.Challenge);
        else
            Write(Output.Pass);
        // TODO if opp is continually stealing we need to figure out who wins the race if we keep taking Tax.
    }

    private void RespondToChallenge(IChallengeable challengedAction)
    {
        if (Cards.Contains(challengedAction.RequiredCard))
            Write(challengedAction.RequiredCard);
        else
            GiveUpDecide();

        if (challengedAction == ChallengeableAction.Tax)
            OustedAsDuke = true;
    }

    private void GiveUpDecide()
    {
        Write(Cards.OrderBy(card => _GiveUpPreferences.IndexOf(card)).Last().GiveUp);

        if (_MyTurn)
            Write(Output.EndTurn);
    }

    private bool ShouldChallenge(IChallengeable prev)
    {
        // Never challenge if we're far enough ahead, always challenge if far enough behind
        if (MyScore > (OppScore + 7))
        {
            return false;
        }
        else if (MyScore < (OppScore - 10))
        {
            return true;
        }
        else
        {
            if (prev == ChallengeableAction.Assassinate)
                return ShouldRandomChallenge(BaseProbabilityToChallenge * 0.5d);
            else if (prev is Block)
                return ShouldRandomChallenge(BaseProbabilityToChallenge * 2d);
            else if (prev == ChallengeableAction.Tax && OppCoin >= 4 && MyCardCount <= 1 && (MyCoin < 7 || OppCardCount > 1))
                return true;
            else
                return ShouldRandomChallenge(BaseProbabilityToChallenge);
        }
    }

    private bool ShouldRandomChallenge(double prob)
    {
        return _Rand.NextDouble() < prob;
    }

    private void WriteRandomValid()
    {
        int index = _Rand.Next(0, ValidOutputs.Count());
        var randomOutput = ValidOutputs.ElementAt(index);
        Write(randomOutput);
    }

    private void Write(Output output)
    {
        Debug.Assert(!_Written || (_MyTurn && output == Output.EndTurn), "If we've already written a value we shouldn't be trying to write another.");
        Debug.Assert(ValidOutputs.Contains(output), "Should only be writing valid outputs to file.");

        File.AppendAllText(FileName, output.Symbol.ToString());
        _Written = true;
    }
}

[DebuggerDisplay("{Symbol}")]
internal class Output
{
    public static readonly Output Pass = new Output() { Symbol = 'p' };
    public static readonly Output Challenge = new Output() { Symbol = 'q' };
    public static readonly Output EndTurn = new Output() { Symbol = '\n' };

    private static readonly Output[] _BaseOutputs = new Output[3] { Pass, Challenge, EndTurn };

    protected Output() { }

    public static IEnumerable<Output> AllOutputs => ChallengeableAction.Actions.Concat(Block.Blocks.Concat(Card.Cards.Concat(GiveUp.GiveUps.Concat(_BaseOutputs))));

    public static IList<Output> ParseSymbols(IEnumerable<char> symbols)
    {
        var parsedOutputs = new List<Output>();
        foreach (var symbol in symbols)
        {
            if (symbol == '\r') continue; // newlines can show up as \r\n so need to skip the \r.
            var matchingOutput = AllOutputs.FirstOrDefault(output => output.Symbol == symbol);
            if (matchingOutput == null)
            {
                throw new InvalidOperationException($"Could not parse Output symbol: \"{symbol}\"");
            }
            parsedOutputs.Add(matchingOutput);
        }
        return parsedOutputs;
    }

    public char Symbol { get; protected set; }
}

internal sealed class Card : Output
{
    public static readonly Card Ambassador = new Card() { Symbol = '~', GiveUp = GiveUp.Ambassador, AvailableAction = ChallengeableAction.Exchange, AvalableBlock = Block.Ambassador };
    public static readonly Card Assassin = new Card() { Symbol = '^', GiveUp = GiveUp.Assassin, AvailableAction = ChallengeableAction.Assassinate };
    public static readonly Card Captain = new Card() { Symbol = '*', GiveUp = GiveUp.Captain, AvailableAction = ChallengeableAction.Steal, AvalableBlock = Block.Captain };
    public static readonly Card Contessa = new Card() { Symbol = '!', GiveUp = GiveUp.Contessa, AvalableBlock = Block.Contessa };
    public static readonly Card Duke = new Card() { Symbol = '$', GiveUp = GiveUp.Duke, AvailableAction = ChallengeableAction.Tax, AvalableBlock = Block.Duke };

    private static readonly Card[] _Cards = new Card[5] { Ambassador, Assassin, Captain, Contessa, Duke };

    private Card() { }

    public static IEnumerable<Card> Cards => _Cards;

    public GiveUp GiveUp { get; private set; }
    public ChallengeableAction AvailableAction { get; private set; }//=> ChallengeableAction.ChallengeableActions.SingleOrDefault(action => action.RequiredCard == this);
    public Block AvalableBlock { get; private set; }// => Block.Blocks.SingleOrDefault(block => block.RequiredCard == this);

    new public static IEnumerable<Card> ParseSymbols(IEnumerable<char> cardSymbols)
    {
        var parsedCards = new List<Card>();
        foreach (var symbol in cardSymbols)
        {
            var matchingCard = Cards.FirstOrDefault(card => card.Symbol == symbol);
            if (matchingCard == null) throw new InvalidOperationException($"Could not parse card symbol: {symbol}");
            parsedCards.Add(matchingCard);
        }
        return parsedCards;
    }
}

internal class Action : Output
{
    public static readonly Action Income = new Action() { Symbol = 'I' };
    public static readonly Action ForeignAid = new Action() { Symbol = 'F', BlockedBy = new Block[1] { Block.Duke } };
    public static readonly Action Coup = new Action() { Symbol = 'C' };

    protected Action() : base() { }

    public IEnumerable<Block> BlockedBy { get; protected set; } = new Block[0];
}

internal sealed class ChallengeableAction : Action, IChallengeable
{
    public static readonly ChallengeableAction Tax = new ChallengeableAction() { Symbol = 'T' };
    public static readonly ChallengeableAction Assassinate = new ChallengeableAction() { Symbol = 'A', BlockedBy = new Block[1] { Block.Contessa } };
    public static readonly ChallengeableAction Exchange = new ChallengeableAction() { Symbol = 'E' };
    public static readonly ChallengeableAction Steal = new ChallengeableAction { Symbol = 'S', BlockedBy = new Block[2] { Block.Ambassador, Block.Captain } };

    private static readonly Action[] _Actions = new Action[7] { Income, ForeignAid, Coup, Tax, Assassinate, Exchange, Steal };
    private static readonly ChallengeableAction[] _ChallengeableActions = new ChallengeableAction[4] { Tax, Assassinate, Exchange, Steal };

    private ChallengeableAction() : base() { }

    public static IEnumerable<Action> Actions => _Actions;
    public static IEnumerable<ChallengeableAction> ChallengeableActions => _ChallengeableActions;

    public Card RequiredCard => Card.Cards.Single(card => card.AvailableAction == this);
}

internal sealed class Block : Output, IChallengeable
{
    public static readonly Block Duke = new Block() { Symbol = 'd' };
    public static readonly Block Ambassador = new Block() { Symbol = 'a' };
    public static readonly Block Captain = new Block() { Symbol = 'c' };
    public static readonly Block Contessa = new Block() { Symbol = 's' };

    private static readonly Block[] _Blocks = new Block[4] { Ambassador, Captain, Contessa, Duke };

    private Block() : base() { }

    public static IEnumerable<Block> Blocks => _Blocks;

    public Card RequiredCard => Card.Cards.Single(card => card.AvalableBlock == this);
    public Action ActionBlocked => ChallengeableAction.Actions.Single(action => action.BlockedBy.Contains(this));
}

internal sealed class GiveUp : Output
{
    public static readonly GiveUp Ambassador = new GiveUp() { Symbol = '_' };
    public static readonly GiveUp Assassin = new GiveUp() { Symbol = '\'' };
    public static readonly GiveUp Captain = new GiveUp() { Symbol = '<' };
    public static readonly GiveUp Contessa = new GiveUp() { Symbol = '=' };
    public static readonly GiveUp Duke = new GiveUp() { Symbol = '0' };

    private static readonly GiveUp[] _GiveUps = new GiveUp[5] { Ambassador, Assassin, Captain, Contessa, Duke };

    private GiveUp() : base() { }

    public static IEnumerable<GiveUp> GiveUps => _GiveUps;

    public Card Card => Card.Cards.Single(card => card.GiveUp == this);
}

internal interface IChallengeable { Card RequiredCard { get; } }

Answer 6

Mask

The Mask is a master of disguise. He prevents opponents from keeping track of his cards by Exchanging every time he acts or blocks. His winning strategy is to take 3 coins as the Duke, then Assassinate.

Compile with go build mask.go, run with ./mask.

package main

import (
    "bytes"
    "io/ioutil"
    "os"
    "strconv"
    "strings"
)

var revealToPunishment = map[byte]byte{'~': '_', '^': '\'', '*': '<', '!': '=', '$': '0'}
var assertedCardMap = map[byte]byte{'A': '^', 'E': '~', 'S': '*', 'T': '$', 'a': '~', 'c': '*', 's': '!', 'd': '$'}

func actWithOneCard(file *os.File, coinCount int, ourCards string) {
    if coinCount >= 7 {
        file.WriteString("C")
    } else if ourCards == "$" {
        file.WriteString("T")
    } else {
        file.WriteString("I\n")
    }
}

func mostRecentClaim(lines [][]byte) byte {
    // If we blocked and were not challenged on the opponent's last turn, return
    // what we claimed to have in the block.
    opponentsLastTurn := lines[len(lines)-1]
    switch b := opponentsLastTurn[len(opponentsLastTurn)-1]; b {
    case 'a', 'c', 's', 'd':
        return b
    }
    // Otherwise, return the first character of our last turn.
    ourLastTurn := lines[len(lines)-2]
    return ourLastTurn[0]
}

func whatWePlanToDoNext(lines [][]byte, coinCount int) string {
    if len(lines) < 2 || mostRecentClaim(lines) == 'E' {
        if coinCount >= 3 {
            return "A"
        } else {
            return "T"
        }
    } else {
        return "E"
    }
}

func ourTurn(file *os.File, coinCount int, ourCards string, lines [][]byte) {
    if len(ourCards) == 1 {
        actWithOneCard(file, coinCount, ourCards)
        return
    }
    file.WriteString(whatWePlanToDoNext(lines, coinCount))
}

func handleChallenge(file *os.File, ourCards string, lines [][]byte) {
    lastLine := lines[len(lines)-1]
    attemptedAction := lastLine[len(lastLine)-2]
    assertedCard := assertedCardMap[attemptedAction]
    for i := range ourCards {
        if ourCards[i] == assertedCard && ourCards[i] != '\x00' {
            file.Write([]byte{assertedCard})
            return
        }
    }
    cardToGiveUp := giveUpCard(ourCards)
    file.Write([]byte{revealToPunishment[cardToGiveUp]})
    switch attemptedAction {
    case 'a', 'c', 'd', 's':
    default:
        file.WriteString("\n")
    }
}

func giveUpCard(ourCards string) byte {
    // If we have a Duke, give up the other card.
    if dukeIndex := strings.Index(ourCards, "$"); -1 < dukeIndex && len(ourCards) == 2 {
        return ourCards[(dukeIndex+1)%2]
    }
    return ourCards[0]
}

func main() {
    filename := os.Args[1]
    coinCount, _ := strconv.Atoi(os.Args[3])
    ourCards := os.Args[4]
    file, _ := os.OpenFile(filename, os.O_RDWR, 0755)
    defer file.Close()

    rawBytes, _ := ioutil.ReadAll(file)
    lines := bytes.Split(rawBytes, []byte{'\n'})
    if len(lines[len(lines)-1]) == 0 {
        lines = lines[:len(lines)-1]
    }
    if len(rawBytes) == 0 {
        file.WriteString("T")
        return
    }
    // Exchange. Prioritize Ambassador, Duke, Assassin.
    if len(ourCards) > 2 {
        var has_ambassador, has_duke, has_assassin bool
        var keptCards string
        for len(ourCards) > 2 {
            var i int
            if i = strings.Index(ourCards, "~"); !has_ambassador && i > -1 {
                keptCards += "~"
                has_ambassador = true
                ourCards = ourCards[:i] + ourCards[i+1:]
            } else if i = strings.Index(ourCards, "$"); !has_duke && i > -1 {
                keptCards += "$"
                has_duke = true
                ourCards = ourCards[:i] + ourCards[i+1:]
            } else if i = strings.Index(ourCards, "^"); !has_assassin && i > -1 {
                keptCards += "^"
                has_assassin = true
                ourCards = ourCards[:i] + ourCards[i+1:]
            } else {
                keptCards += ourCards[:1]
                ourCards = ourCards[1:]
            }
        }
        ourCards = keptCards
        os.Stdout.WriteString(ourCards)
    }
    switch rawBytes[len(rawBytes)-1] {
    case '\n':
        ourTurn(file, coinCount, ourCards, lines)
    // Opponent Couped us. Give up a card.
    case 'C':
        file.Write([]byte{revealToPunishment[giveUpCard(ourCards)]})
    // Opponent blocked, or we Assassinated/Couped them. End our turn.
    case 'a', 'c', 'd', 's', 'p', '_', '\'', '<', '=', '0':
        file.WriteString("\n")
    case 'q':
        handleChallenge(file, ourCards, lines)
    // Opponent did something blockable, block it.
    case 'F':
        file.WriteString("d")
    case 'A':
        file.WriteString("s")
    case 'S':
        if strings.Contains(ourCards, "*") {
            file.WriteString("c")
        } else {
            file.WriteString("a")
        }
    // Opponent took some other action. Let it pass.
    default:
        file.WriteString("p")
    }
}

Answer 7

Rando Aggro Lawyer

Similar to the lawyer, it only does legal things. However it Assassinates, coups earlier, and it chooses some actions randomly (like when to Challenge).

#! /usr/bin/env python3
import sys
import random

_, filename, othercoins, mycoins, mycards = sys.argv[:5]


def give_card():
    if "~" in mycards: # give up Ambassador
        return "_"
    if "!" in mycards: # give up Contessa
        return "="
    if "^" in mycards: # give up Assassin
        return "'"
    if "*" in mycards: # give up Captain
        return "<"
    return "0" # give up Duke


with open(filename, "r+") as history:
    line = "\n"
    for a in history:
        line = a # get the last line of the file
    print("{}, {}, {}, {}".format(line, othercoins, mycoins, mycards))
    if line.endswith("\n"): # it has an endline, eg this is a new action
        if int(mycoins) >= 7:
            history.write("C") # coup if I have to
        elif int(mycoins) >= 3 and "^" in mycards:
            history.write("A") # assassinate if I can
        elif "*" in mycards and int(othercoins) > 0:
            history.write("S") # steal if i can
        elif "$" in mycards:
            history.write("T") # tax if i can
        elif random.randint(0,1):
            history.write("F") # foreign aid 50% of the time
        else:
            history.write("I\n") # income
    elif line == "F": # they tried to foreign aid
        if "$" in mycards:
             history.write("d") # block if i can
        else:
             history.write("p")
    elif line == "C": # they coup, sad
        history.write(give_card())
    elif line == "E": # they Exchange
        if random.randint(0,1):
            history.write("q") # challenge 50% of the time
        else: 
            history.write("p") 
    elif line == "T": # they tax
        if random.randint(0,1):
            history.write("q") # challenge 50% of the time
        else: 
            history.write("p") 
    elif line == "A": # they assassinate
        if "!" in mycards:
            history.write("s") # block with contessa if i can
        elif random.randint(0,1):
            history.write("q") # challenge 50% of the time
        else: 
            history.write(give_card()) # otherwise give up a card
    elif line == "S": # they steal
        if "~" in mycards:
            history.write("a") # block with ambassador if i can
        elif "*" in mycards:
            history.write("c") # block with captain if i can
        elif random.randint(0,1):
            history.write("q") # challenge 50% of the time
        else:
            history.write("p")
    elif line.endswith("d") and random.randint(0,1): # they block my foreign aid
        history.write("q") # challenge 50% of the time
    elif line.endswith("a") and random.randint(0,1): # they block as ambassador
        history.write("q") # challenge 50% of the time
    elif line.endswith("c") and random.randint(0,1): # they block as captain
        history.write("q") # challenge 50% of the time
    elif line.endswith("s") and random.randint(0,1): # they block as contessa
        history.write("q") # challenge 50% of the time
    elif line.endswith("sq"): # they challenged my contessa block
        history.write("!") # reveal that i have contessa (no condition because i never lie block)
    elif line.endswith("aq"): # they challenge my Ambassador block
        history.write("~") # reveal that i have a captain (no condition because i never lie block)
    elif line.endswith("cq"): # they challenged my Captain block
        history.write("*") # reveal that I have a Captain (no condition because i never lie block)
    elif line.endswith("dq"): # they challenge my Duke block
        history.write("$") # reveal that I have a Duke (no condition because i never lie block)
    elif line.endswith("Tq"): # they challenge my Tax 
        history.write("$") # reveal that I have a Duke (no condition because i fake tax)
    elif line.endswith("Aq"): # they challenge my assassinate
        history.write("^") # reveal that I had an Assasin
    elif line.endswith("Sq"): # they challenge my steal
        history.write("*") # reveal that I have a Captain
    elif line[-1] in "~^*!$": # they respond to my challenge successfully
        history.write(give_card()) # give up card
        if line[-3] in "acds":
            history.write("\n")
    else:
        history.write("\n")
    history.seek(0)
    print("out")
    print(history.read())

Answer 8

Gambler

The gambler has a fleshed out strategy but trusts his gut when a situation isn't accounted for in his winning strategy. He tries to steal a lot and coups/assassinates whenever possible.

Written in Python3:

import sys
import random
import time

random.seed(time.time())  # lets keep it rather random

_, filename, othercoins, mycoins, mycards = sys.argv[:5]
legal_actions = sys.argv[5:]

othercoins = int(othercoins)
mycoins = int(mycoins)

income = 'I\n'

foreign_aid, coup, exchange, tax, assassinate, steal, block_aid, \
block_steal_amb, block_steal_cap, block_assassinate, \
pass_challange, do_challenge = "FCETASdacspq"


loosing_actions = "_'<=0"
loose_ambassador, loose_assassin, loose_captain, loose_contessa, loose_duke = loosing_actions
have_ambassador, have_assassin, have_captain, \
have_contessa, have_duke = "~^*!$"

actions_dict = {
    exchange: loose_ambassador, tax: loose_duke, assassinate: loose_assassin, steal: loose_captain,
    block_aid: loose_duke, block_steal_amb: loose_ambassador, block_steal_cap: loose_captain, block_assassinate: loose_contessa
}


def guess_opponents_hand():
    # get number of each card still in play and not in hand
    card_counts = [3] * 5
    card_give_up = list("_'<=0")
    with open(filename, 'r') as history:
        while True:
            line = history.readline()
            if not line:
                break
            for card in card_give_up:
                if card in line:
                    card_counts[card_give_up.index(card)] -= 1

    have_cards = list("~^*!$")

    if sum(card_counts) == 15:
        num_cards = 2
    elif sum(card_counts) == 14:
        if len(mycards) == 1:
            num_cards = 2
        else:
            num_cards = 1
    else:
        num_cards = 1

    for card in mycards:
        card_counts[have_cards.index(card)] -= 1

    # randomly sample a hand for the opponent
    card_1 = sample_from_probabilities([i / sum(card_counts) for i in card_counts], card_give_up)
    if num_cards == 1:
        return card_1
    card_counts[card_give_up.index(card_1)] -= 1
    return card_1 + sample_from_probabilities([i / sum(card_counts) for i in card_counts], card_give_up)


def sample_from_probabilities(success_probabilities, actions):
    # weighted random
    return random.choices(actions, success_probabilities)[0]

def get_prev_char(line, x=1):
    try:
        return line[-1*x]
    except:
        return ""


def get_prev_line(lines):
    try:
        return lines[-2]
    except:
        return []


def give_card(not_swap=True):
    if have_ambassador in mycards:  # give up Ambassador
        return loose_ambassador if not_swap else have_ambassador
    if have_contessa in mycards:  # give up Contessa
        return loose_contessa if not_swap else have_contessa
    if have_assassin in mycards:  # give up Assassin
        return loose_assassin if not_swap else have_assassin
    if have_duke in mycards:  # give up duke
        return loose_duke if not_swap else have_duke
    return loose_captain if not_swap else have_captain  # give up captain


action = legal_actions[0]  # failsafe
with open(filename, 'r') as file:
    all_lines = file.readlines()
    try:
        curr_line = all_lines[-1]
    except IndexError:
        curr_line = ""

obvious_actions = ['C', '~', '^', '*', '!', '$']  # borrowed from Brilliand
obvious = list(set(obvious_actions).intersection((set(legal_actions))))


otherhand = guess_opponents_hand()


# take care of easy choices
if obvious:
    action = coup if coup in obvious else obvious[0]
elif len(set(list(loosing_actions)).intersection(set(legal_actions))) == len(set(legal_actions)):
    action = give_card()
elif len(set([i+'\n' for i in list(loosing_actions)]).intersection(set(legal_actions))) == len(set(legal_actions)):
    action = give_card() + '\n'
elif len(legal_actions) == 1:
    action = legal_actions[0]
elif assassinate in legal_actions and have_assassin in mycards:  # if we can legally assassinate, we try to
    action = assassinate
elif steal in legal_actions and othercoins > 1 and have_captain in mycards:  # we steal when we can or have to prevent a killing coup
    action = steal
elif steal in legal_actions and 7 <= othercoins <= 8 and len(mycards) == 1 and have_assassin not in mycards:
    action = steal
elif block_assassinate in legal_actions and have_contessa in mycards:
    action = block_assassinate
elif block_aid in legal_actions and have_duke in mycards:
    action = block_aid
elif block_steal_cap in legal_actions and have_captain in mycards:
    action = block_steal_cap
elif block_steal_amb in legal_actions and have_ambassador in mycards:
    action = block_steal_amb
elif tax in legal_actions and have_duke in mycards:
    action = tax
elif foreign_aid in legal_actions and foreign_aid in get_prev_line(all_lines):  # opponent wouldn't foreign aid with a duke
    action = foreign_aid
elif block_aid in legal_actions:
    if loose_duke not in otherhand and len(mycards) > 1:
        action = block_aid
    else:
        action = pass_challange if pass_challange in legal_actions else "\n"


elif do_challenge in legal_actions:
    no_challenge = pass_challange if pass_challange in legal_actions else "\n"
    action = do_challenge if len(mycards) > 1 else no_challenge  # failsafe
    if get_prev_char(curr_line) == block_aid and (not loose_duke in otherhand or len(mycards) > 1):  # we don't think opponent has a duke
        action = do_challenge
    elif get_prev_char(curr_line) == exchange:
        action = pass_challange
    elif block_assassinate in legal_actions:
        if len(mycards) == 1:
            if loose_assassin in otherhand and loose_contessa not in otherhand:
                action = block_assassinate
            elif loose_assassin not in otherhand:
                action = do_challenge
            else:
                action = random.choice([block_assassinate, do_challenge])
        else:
            action = give_card()
    elif block_steal_amb in legal_actions:
        if len(mycards) > 1 and 7 <= mycoins <= 8:
            if loose_captain in otherhand:
                probs = [0.4, 0.4, 0.2]
            else:
                probs = [0.2, 0.2, 0.6]

            action = sample_from_probabilities(probs, [block_steal_amb, block_steal_cap, do_challenge])
        elif len(mycards) == 1 and len(otherhand) == 1 and 7 <= mycoins <= 8:
            action = do_challenge  # worth the risk if we defend a winning move
        else:
            action = do_challenge if len(mycards) > 1 else pass_challange  # failsafe
            # go with default

    elif get_prev_char(curr_line) == tax and loose_duke not in otherhand and len(mycards) > 1:
        action = do_challenge
    elif get_prev_char(curr_line) == exchange:
        action = pass_challange
    elif get_prev_char(curr_line) in {block_steal_cap, block_steal_amb, block_aid, block_assassinate}:
        if get_prev_char(curr_line) == block_aid:
            action = do_challenge
        elif get_prev_char(curr_line) == block_assassinate:
            if len(otherhand) == 1 and loose_contessa not in otherhand:
                action = do_challenge
        elif get_prev_char(curr_line) == block_steal_amb:
            action = pass_challange if pass_challange in legal_actions else "\n"

# other choices shall be weighted random choices
elif len(set(legal_actions).intersection({assassinate, steal, tax, income, exchange})) >= 3:
    # decide between aggro ass, aggro steal, aggro Tax, Income, Exchange
    assumed_values = [(assassinate in legal_actions) * (loose_assassin not in otherhand) * 0.1 * len(mycards) * (len(otherhand) - 1) * (mycoins >= 3),
                      (othercoins > 1) * ((othercoins > 5 * 0.3) + othercoins * 0.05) * (len(mycards) - 1) * (loose_ambassador not in otherhand),
                      0.1 * (loose_duke not in otherhand) * (len(mycards) - 1)**(len(otherhand) - 1),
                      0.3,
                      (have_ambassador in mycards) * 0.5/len(mycards)
                      ]
    normalized_probs = [float(i) / sum(assumed_values) for i in assumed_values]
    actions = [assassinate, steal, tax, income, exchange]
    action = sample_from_probabilities(normalized_probs, actions)
elif get_prev_char(curr_line) == do_challenge or get_prev_char(curr_line) == coup:
    # we lost a challenge or coup
    card = give_card()
    action = card if card in legal_actions else action
else:
    # We missed a case. This shouldn't happen. Please tell me so I can fix it!
    # Note: A failsafe always taking a legal action is in place, so please comment out the error raising after telling me :)
    raise RuntimeError("Please tell me this happened, give me the history file, comment out this line, "
                       "and replay. THANKS!")
    pass

with open(filename, "a") as history:
    history.write(str(action))

if len(mycards) > 2:
    mycards = mycards.replace(give_card(False), "", 1)
    mycards = mycards.replace(give_card(False), "", 1)
    print(mycards)

Statistician

Knows his winning strategy, just like the gambler, but always trusts maximum probabilities instead of randomly sampling from them.

import sys
import random
import time

random.seed(time.time())  # lets keep it rather random

_, filename, othercoins, mycoins, mycards = sys.argv[:5]
legal_actions = sys.argv[5:]

othercoins = int(othercoins)
mycoins = int(mycoins)

income = 'I\n'

foreign_aid, coup, exchange, tax, assassinate, steal, block_aid, \
block_steal_amb, block_steal_cap, block_assassinate, \
pass_challange, do_challenge = "FCETASdacspq"


loosing_actions = "_'<=0"
loose_ambassador, loose_assassin, loose_captain, loose_contessa, loose_duke = loosing_actions
have_ambassador, have_assassin, have_captain, \
have_contessa, have_duke = "~^*!$"

actions_dict = {
    exchange: loose_ambassador, tax: loose_duke, assassinate: loose_assassin, steal: loose_captain,
    block_aid: loose_duke, block_steal_amb: loose_ambassador, block_steal_cap: loose_captain, block_assassinate: loose_contessa
}


def guess_opponents_hand():
    # get number of each card still in play and not in hand
    card_counts = [3] * 5
    card_give_up = list("_'<=0")
    with open(filename, 'r') as history:
        while True:
            line = history.readline()
            if not line:
                break
            for card in card_give_up:
                if card in line:
                    card_counts[card_give_up.index(card)] -= 1

    have_cards = list("~^*!$")

    if sum(card_counts) == 15:
        num_cards = 2
    elif sum(card_counts) == 14:
        if len(mycards) == 1:
            num_cards = 2
        else:
            num_cards = 1
    else:
        num_cards = 1

    for card in mycards:
        card_counts[have_cards.index(card)] -= 1

    # randomly sample a hand for the opponent
    card_1 = sample_from_probabilities([i / sum(card_counts) for i in card_counts], card_give_up)
    if num_cards == 1:
        return card_1
    card_counts[card_give_up.index(card_1)] -= 1
    return card_1 + sample_from_probabilities([i / sum(card_counts) for i in card_counts], card_give_up)


def sample_from_probabilities(success_probabilities, actions):
    # statistical max, decide randomly on equivalent probabilities
    max_prob = max(success_probabilities)
    indicies = []
    idx = 0
    for i in success_probabilities:
        if i == max_prob:
            indicies.append(idx)
        idx += 1
    choice = random.choice(indicies)
    return actions[choice]


def get_prev_char(line, x=1):
    try:
        return line[-1*x]
    except:
        return ""


def get_prev_line(lines):
    try:
        return lines[-2]
    except:
        return []


def give_card(not_swap=True):
    if have_ambassador in mycards:  # give up Ambassador
        return loose_ambassador if not_swap else have_ambassador
    if have_contessa in mycards:  # give up Contessa
        return loose_contessa if not_swap else have_contessa
    if have_assassin in mycards:  # give up Assassin
        return loose_assassin if not_swap else have_assassin
    if have_duke in mycards:  # give up duke
        return loose_duke if not_swap else have_duke
    return loose_captain if not_swap else have_captain  # give up captain


action = legal_actions[0]  # failsafe
with open(filename, 'r') as file:
    all_lines = file.readlines()
    try:
        curr_line = all_lines[-1]
    except IndexError:
        curr_line = ""

obvious_actions = ['C', '~', '^', '*', '!', '$']  # borrowed from Brilliand
obvious = list(set(obvious_actions).intersection((set(legal_actions))))


otherhand = guess_opponents_hand()


# take care of easy choices
if obvious:
    action = coup if coup in obvious else obvious[0]
elif len(set(list(loosing_actions)).intersection(set(legal_actions))) == len(set(legal_actions)):
    action = give_card()
elif len(set([i+'\n' for i in list(loosing_actions)]).intersection(set(legal_actions))) == len(set(legal_actions)):
    action = give_card() + '\n'
elif len(legal_actions) == 1:
    action = legal_actions[0]
elif assassinate in legal_actions and have_assassin in mycards:  # if we can legally assassinate, we try to
    action = assassinate
elif steal in legal_actions and othercoins > 1 and have_captain in mycards:  # we steal when we can or have to prevent a killing coup
    action = steal
elif steal in legal_actions and 7 <= othercoins <= 8 and len(mycards) == 1 and have_assassin not in mycards:
    action = steal
elif block_assassinate in legal_actions and have_contessa in mycards:
    action = block_assassinate
elif block_aid in legal_actions and have_duke in mycards:
    action = block_aid
elif block_steal_cap in legal_actions and have_captain in mycards:
    action = block_steal_cap
elif block_steal_amb in legal_actions and have_ambassador in mycards:
    action = block_steal_amb
elif tax in legal_actions and have_duke in mycards:
    action = tax
elif foreign_aid in legal_actions and foreign_aid in get_prev_line(all_lines):  # opponent wouldn't foreign aid with a duke
    action = foreign_aid
elif block_aid in legal_actions:
    if loose_duke not in otherhand and len(mycards) > 1:
        action = block_aid
    else:
        action = pass_challange if pass_challange in legal_actions else "\n"


elif do_challenge in legal_actions:
    no_challenge = pass_challange if pass_challange in legal_actions else "\n"
    action = do_challenge if len(mycards) > 1 else no_challenge  # failsafe
    if get_prev_char(curr_line) == block_aid and (not loose_duke in otherhand or len(mycards) > 1):  # we don't think opponent has a duke
        action = do_challenge
    elif get_prev_char(curr_line) == exchange:
        action = pass_challange
    elif block_assassinate in legal_actions:
        if len(mycards) == 1:
            if loose_assassin in otherhand and loose_contessa not in otherhand:
                action = block_assassinate
            elif loose_assassin not in otherhand:
                action = do_challenge
            else:
                action = random.choice([block_assassinate, do_challenge])
        else:
            action = give_card()
    elif block_steal_amb in legal_actions:
        if len(mycards) > 1 and 7 <= mycoins <= 8:
            if loose_captain in otherhand:
                probs = [0.4, 0.4, 0.2]
            else:
                probs = [0.2, 0.2, 0.6]

            action = sample_from_probabilities(probs, [block_steal_amb, block_steal_cap, do_challenge])
        elif len(mycards) == 1 and len(otherhand) == 1 and 7 <= mycoins <= 8:
            action = do_challenge  # worth the risk if we defend a winning move
        else:
            action = do_challenge if len(mycards) > 1 else pass_challange  # failsafe
            # go with default

    elif get_prev_char(curr_line) == tax and loose_duke not in otherhand and len(mycards) > 1:
        action = do_challenge
    elif get_prev_char(curr_line) == exchange:
        action = pass_challange
    elif get_prev_char(curr_line) in {block_steal_cap, block_steal_amb, block_aid, block_assassinate}:
        if get_prev_char(curr_line) == block_aid:
            action = do_challenge
        elif get_prev_char(curr_line) == block_assassinate:
            if len(otherhand) == 1 and loose_contessa not in otherhand:
                action = do_challenge
        elif get_prev_char(curr_line) == block_steal_amb:
            action = pass_challange if pass_challange in legal_actions else "\n"

# other choices shall be weighted random choices
elif len(set(legal_actions).intersection({assassinate, steal, tax, income, exchange})) >= 3:
    # decide between aggro ass, aggro steal, aggro Tax, Income, Exchange
    assumed_values = [(assassinate in legal_actions) * (loose_assassin not in otherhand) * 0.1 * len(mycards) * (len(otherhand) - 1) * (mycoins >= 3),
                      (othercoins > 1) * ((othercoins > 5 * 0.3) + othercoins * 0.05) * (len(mycards) - 1) * (loose_ambassador not in otherhand),
                      0.1 * (loose_duke not in otherhand) * (len(mycards) - 1)**(len(otherhand) - 1),
                      0.3,
                      (have_ambassador in mycards) * 0.5/len(mycards)
                      ]
    normalized_probs = [float(i) / sum(assumed_values) for i in assumed_values]
    actions = [assassinate, steal, tax, income, exchange]
    action = sample_from_probabilities(normalized_probs, actions)
elif get_prev_char(curr_line) == do_challenge or get_prev_char(curr_line) == coup:
    # we lost a challenge or coup
    card = give_card()
    action = card if card in legal_actions else action
else:
    # We missed a case. This shouldn't happen. Please tell me so I can fix it!
    # Note: A failsafe always taking a legal action is in place, so please comment out the error raising after telling me :)
    raise RuntimeError("Please tell me this happened, give me the history file, comment out this line, "
                       "and replay. THANKS!")
    pass

with open(filename, "a") as history:
    history.write(str(action))

if len(mycards) > 2:
    mycards = mycards.replace(give_card(False), "", 1)
    mycards = mycards.replace(give_card(False), "", 1)
    print(mycards)