Regex in python: is it possible to get the match, replacement, and final string?

Question

For doing a regex substitution, there are three things that you give it:

• The match pattern
• The replacement pattern
• The original string
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Answer 1

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.