Skip or delete lines between two keywords in a file using python

Question

The problem is I need to skip or delete all the lines between the two keywords in a file and the keyword pair will appear many times in the file.The file looks something like this

.
.
..........
..........
Hello world
..........
..........
welcome
.
.
.
..........
..........
Hello world
..........
..........
welcome
.
.
.
.........
.........
Hello world
..........
..........
welcome
.
.
.
..........
..........

Here the contents between Hello world and welcome are to be deleted (including those keywords). Please help me out with this.