What's the Python equivalent of $1 in Perl, or any other special variables in regular expressions?

Question

I've just made the switch from Perl to Python and am disappointed by the re module. I'm looking for the equivalent of $1 in Python, or any other special variables in regular expressions. In Perl I would use this: $_ = "<name>Joe</name>"; s/<(.)>(.)<[/](.*)>/$2/; I'm trying to do the same in Python. Thanks!

Answer 1

You can also use the \2 in the back ref or match group in Python.

Such as this:

>>> re.sub(r'(\w+) (\w+)',r'\2 \1','Joe Bob')
'Bob Joe'

Or named substitutions (a Python innovation later ported to Perl):

>>> re.sub(r'(?P<First>\w+) (?P<Second>\w+)',r'\g<Second> \g<First>','Joe Bob')
'Bob Joe'
>>> ma=re.search(r'(?P<First>\w+) (?P<Second>\w+)','George Bush')
>>> ma.group(1)
'George'
>>> ma.group('Second')
'Bush'

But, admittedly, Python re module is a little weak in comparison to recent Perl's.

For a first class regex module, install the newer regex module. It is scheduled to by part of Python 3.4 and is very good.