regex sub with pattern reference

Question

lets say I have the following string:

s = """hi my name is 'Ryan' and I like to 'program' in "Python" the best"""

I would like to run a re.sub that would change the following string to:

"""hi my name is '{0}' and I like to '{1}' in "{2}" the best"""

This would let me save content, but have a reference to it so that I could add the original content back in.

note: I use the following code to grab all of the items in quotes so I would loop through this to make reference to the numbers

items = re.findall(r'([\'"])(.*?)\1',s)

So how can I make it so the sub will recognize the number instance so I can create this kind of reference?

falsetru · Accepted Answer · 2013-09-11 16:11:37Z

4

Use re.sub with callback:

>>> import itertools
>>> import re
>>> s = """hi my name is 'Ryan' and I like to 'program' in "Python" the best"""
>>> c = itertools.count(1)
>>> replaced = re.sub(r'([\'"])(.*?)\1', lambda m: '{0}{{{1}}}{0}'.format(m.group(1), next(c)), s)
>>> print(replaced)
hi my name is '{1}' and I like to '{2}' in "{3}" the best

Used itertools.count to generate numbers:

>>> it = itertools.count(1)
>>> next(it)
1
>>> next(it)
2
>>> next(it)
3

edited Sep 11, 2013 at 16:11

answered Sep 11, 2013 at 16:04

falsetru

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3 Comments

Ryan Saxe Over a year ago

I have to go to a class now, but i'll accept your answer when I get back in a couple hours

Ryan Saxe Over a year ago

if I wanted to use other symbols to wrap other than curly brackets, how do I? when I change the code to make it for < those kinds of brackets, i get the following error:

File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/re.py", line 151, in sub     return _compile(pattern, flags).sub(repl, string, count)   File "<stdin>", line 5, in <lambda> KeyError: '<1>'

falsetru Over a year ago

Try '{0}({1}){0}', {0}*{1}*{0}, .... Curly braces was escaped because of Format String Syntax.

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