What is \1 here?
Ned Batchelder
ned at nedbatchelder.com
Tue Nov 11 06:52:15 EST 2014
On 11/11/14 4:18 AM, satishmlmlml at gmail.com wrote:
> What does \1 do in the following piece of code(fourth line)?
> import re
> print(re.sub('[ABC]', '*', 'XAXAXBXBXCXC'))
> print(re.sub('[ABC]_', '*', 'XA-XA_XB-XB_XC-XC_'))
> print(re.sub('(.) spam', 'spam\\1', 'x spam, y spam'))
> def mapper(matchobj):
> return 'spam' + matchobj.group(1)
> print(re.sub('(.) spam', mapper, 'x spam, y spam'))
>
Maybe you can't tell from the reception you're getting here: People are
growing tired of your questions about basic Python behavior. They want
you to find a way to learn for yourself. You're asking about regular
expressions. The Python docs have an extensive page detailing how they
work: https://docs.python.org/3/library/re.html
You need to learn how to find this stuff out for yourself. Ben Finney
even gave you a pointer to a helpful site for experimenting with
regexes: http://pythex.org/
--
Ned Batchelder, http://nedbatchelder.com
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