flexible find and replace ?

[John Machin]

On Feb 17, 7:10 am, OdarR <Olivier.Da... at gmail.com> wrote:
> Hi guys,
>
> how would you do a clever find and replace, where the value replacing
> the tag
> is changing on each occurence ?
>
> ".......TAG............TAG................TAG..........TAG....."
>
> is replaced by this :
>
> ".......REPL01............REPL02................REPL03..........REPL04..."
>
> A better and clever method than this snippet should exist I hope :
>
> counter = 1
> while 'TAG' in mystring:
>     mystring=mystring.replace('TAG', 'REPL'+str(counter), 1)
>     counter+=1
>     ...
>
> (the find is always re-starting at the string beginning, this is not
> efficient.
>
> any ideas ? thanks,

C:\junk>type fancyrepl.py
def fancyrepl(tag, replfunc, input_string):
    count = 0
    pieces = []
    pos = 0
    taglen = len(tag)
    while 1:
        try:
            newpos = input_string.index(tag, pos)
        except ValueError:
            pieces.append(input_string[pos:])
            return ''.join(pieces)
        pieces.append(input_string[pos:newpos])
        count += 1
        pieces.append(replfunc(count))
        pos = newpos + taglen

tests = [
    '',
    'XXX',
    'XXXXXX',
    'abcdeXXX',
    'XXXfghij',
    'abcdeXXXfghij',
    'abcdeXXXfghijXXXpqrst',
    ]

for test in tests:
    print ' <', repr(test)
    result = fancyrepl('XXX', lambda n: 'SUB%d' % n, test)
    print ' >', repr(result)

C:\junk>fancyrepl.py
 < ''
 > ''
 < 'XXX'
 > 'SUB1'
 < 'XXXXXX'
 > 'SUB1SUB2'
 < 'abcdeXXX'
 > 'abcdeSUB1'
 < 'XXXfghij'
 > 'SUB1fghij'
 < 'abcdeXXXfghij'
 > 'abcdeSUB1fghij'
 < 'abcdeXXXfghijXXXpqrst'
 > 'abcdeSUB1fghijSUB2pqrst'

HTH,
John