Removing substring from string

[wrobl1rt]

I am trying to remove a specific substring from a string... Here are the doctests that are supposed to pass. I'm just absolutely stumped. Can someone point me in the right direction on where to start?

def remove(sub, s):

"""
>>> remove('an', 'banana')
'bana'
>>> remove('cyc', 'bicycle')
'bile'
>>> remove('iss', 'Mississippi')
'Mippi'
"""


def remove_all(sub, s):
"""
>>> remove('an', 'banana')
'ba'
>>> remove('cyc', 'bicycle')
'bile'
>>> remove('iss', 'Mississippi')
'Mippi'
"""


if __name__ == '__main__':
import doctest
doctest.testmod ()

[bvdet]

I don't understand the question. Surely it's not as simple as this:

>>> 'banana'.replace('an', '')
'ba'
>>> 'banana'.replace('an', '', 1)
'bana'
>>> 'Mississippi'.replace('iss', '')
'Mippi'
>>> 'Mississippi'.replace('iss', '', 1)
'Missippi'
>>>

[mrkozma]

This is one solution for remove_all:

import string

def remove_all(substr, str):
    index = 0
    length = len(substr)
    while string.find(str, substr) != -1:
        index = string.find(str, substr)
        str = str[0:index] + str[index+length:]
    return str