[Python-Dev] regex module

Terry Reedy tjreedy at udel.edu
Wed Jan 13 00:05:12 CET 2010

On 1/12/2010 5:10 PM, MRAB wrote:
> Hi all,
> I'm back on the regex module after doing other things and I'd like your
> opinion on a number of matters:
> Firstly, the current re module has a bug whereby it doesn't split on
> zero-width matches. The BDFL has said that this behaviour should be
> retained by default in case any existing software depends on it. My
> question is: should my regex module still do this for Python 3?
> Speaking personally, I'd like it to behave correctly, and Python 3 is
> the version where backwards-compatibility is allowed to be broken.

Are you writing a new module with a new name? If so, do you expect it to 
replace or augment re? (This is the same question as for optparse vs. 
argparse, which I understand to not yet be decided.)
> Secondly, Python 2 is reaching the end of the line and Python 3 is the
> future. Should I still release a version that works with Python 2? I'm
> thinking that it could be confusing if new regex module did zero-width
> splits correctly in Python 3 but not in Python 2. And also, should I
> release it only for Python 3 as a 'carrot'?

2.7 is in alpha with no plans for 2.8, so unless you finish real soon, 
2.7 stdlib is already out. A new engine should get some community 
testing before going in the stdlib. Even 3.2 beta is not that far off 
(8-9 months?) Do *you* want to do the extra work for a 2.x release on PyPI?

> Finally, the module allows some extra backslash escapes, eg \g<name>, in
> the pattern. Should it treat ill-formed escapes, eg \g, as it would have
> treated them in the re module?

What does re do with analogous cases?

Terry Jan Reedy

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