Question

I know how to make string replacements in Python but I need a way to replace only if the sequence is located at the end of the word.

For example:

Rule: at → ate

So cat is changed to cate.

But attorney stays unchanged.

Answer 1

A regex can do that with ease:

import re

regx = re.compile('at\\b')

ch = 'the fat cat was impressed by all the rats gathering at one corner of the great room'

print ch
print regx.sub('ATU',ch)

Result:

the fat cat was impressed by all the rats gathering at one corner of the great room
the fATU cATU was impressed by all the rats gathering ATU one corner of the greATU room

With regexes, we can perform very complicated tasks.

For example, replacing several kinds of strings with a particular replacement for each, thanks to the use of a callback function (here named repl, that receives catched MatchObjects)

import re

regx = re.compile('(at\\b)|([^ ]r(?! ))')

def repl(mat, dic = {1:'ATU',2:'XIXI'}):
    return dic[mat.lastindex]

ch = 'the fat cat was impressed by all the rats gathering at one corner of the great room'

print ch
print regx.sub(repl,ch)

Result:

the fat cat was impressed by all the rats gathering at one corner of the great room
the fATU cATU was imXIXIessed by all the rats gathXIXIing ATU one cXIXIner of the XIXIeATU room