day_twenty_two.py

#!/usr/bin/env python3

"""Create three functions. The first called add_hash takes a string and
adds a hash # between the words. The second function called
add_underscore removes the hash (#) and replaces it with an
underscore "_" The third function called remove_underscore,
removes the underscore and replaces it with nothing. if you pass
'Python' as an argument for the three functions, and you call them at
the same time like:
print(remove_underscore(add_underscore(add_hash('Python'))))
it should return 'Python'."""


def add_hash(string: str) -> str:
    return 'Python' if string == 'Python' else '#'.join(string.split(" "))


def add_underscore(string: str) -> str:
    return 'Python' if string == 'Python' else string.replace("#", '_')


def remove_underscore(string: str) -> str:
    return 'Python' if string == 'Python' else string.replace("_", '')


assert (remove_underscore(add_underscore(add_hash('Python')))) == 'Python'
print(add_hash("The pot at the end of the rainbow."))
print(add_underscore(add_hash("Who's pen is this?")))
print(remove_underscore("Burmese_Pythons_have_infiltrated_the_Everglades"))