How can I replace certain string in a string in Python?

Question

I am trying to write two procedures to replace matched strings in a string in python. And I have to write two procedures.

def matched_case(old new): .........

note: inputs are two strings, it returns a replacement converter.

def replacement(x,another_string): ..........

note:inputs are a converter from previous procedure, and a string. It returns the result of applying the converter to the input string.

for example:

a = matched_case('mm','m')
print replacement(a, 'mmmm')
it should return m

another example:

R = matched_case('hih','i')
print replacement(R, 'hhhhhhihhhhh')
it should return hi

I am not sure how can I use loop to do the whole thing. Thanks so much for anyone can give a hint.

Answer 1

def subrec(pattern, repl, string):
    while pattern in string:
        string = string.replace(pattern, repl)
    return string

foo('mm', 'm', 'mmmm') return m

foo('hih', 'i', 'hhhhhhihhhhh') return hi

Answer 2

Something on the lines of the below might help:

def matched_case(x,y):
    return x, lambda param: param.replace(x,y)

def replacement(matcher, s):
    while matcher[0] in s:
        s = matcher[1](s)
    return s

print replacement(matched_case('hih','i'), 'hhhhhhihhhhh')
print replacement(matched_case('mm','m'), 'mmmm')

OUTPUT:

hi
m

matched_case(..) returns a replacement-converter, so it is best represented using a lambda (anonymous function to put it simply). This anonymous function wraps up the string to the found and the code that actually replaces it.