For doing a regex substitution, there are three things that you give it:
class Replacement(object):
def __init__(self, replacement):
self.replacement = replacement
self.matched = None
self.replaced = None
def __call__(self, match):
self.matched = match.group(0)
self.replaced = match.expand(self.replacement)
return self.replaced
>>> repl = Replacement('not the \\1')
>>> re.sub('(orig.*?l)', repl, 'This is the original string.')
'This is the not the original string.'
>>> repl.matched
'original'
>>> repl.replaced
'not the original'
Edit: as @F.J has pointed out, the above will remember only the last match/replacement. This version handles multiple occurrences:
class Replacement(object):
def __init__(self, replacement):
self.replacement = replacement
self.occurrences = []
def __call__(self, match):
matched = match.group(0)
replaced = match.expand(self.replacement)
self.occurrences.append((matched, replaced))
return replaced
>>> repl = Replacement('[\\1]')
>>> re.sub('\s(\d)', repl, '1 2 3')
'1[2][3]'
>>> for matched, replaced in repl.occurrences:
....: print matched, '=>', replaced
....:
2 => [2]
3 => [3]
I looked at the documentation and it seems like you can pass a function reference into the re.sub
:
import re
def re_sub_verbose(pattern, replace, string):
def substitute(match):
print 'Matched:', match.group(0)
print 'Replacing with:', match.expand(replace)
return match.expand(replace)
result = re.sub(pattern, substitute, string)
print 'Final string:', result
return result
And I get this output when running re_sub_verbose("(orig.*?l)", "not the \\1", "This is the original string.")
:
Matched: original
Replacing with: not the original
This is the not the original string.