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Title: "Default" word boundaries for Unicode data?
Type: enhancement Stage:
Components: Regular Expressions Versions: Python 3.2, Python 2.7
Status: closed Resolution: works for me
Dependencies: Superseder:
Assigned To: Nosy List: RegEx4All, amaury.forgeotdarc, ezio.melotti, loewis, mrabarnett
Priority: normal Keywords:

Created on 2009-11-03 04:22 by RegEx4All, last changed 2022-04-11 14:56 by admin. This issue is now closed.

Messages (6)
msg94856 - (view) Author: daniel mccloy (RegEx4All) Date: 2009-11-03 04:21
Regarding UTS #18 (Unicode Standards for RegEx Engines), which can be
found at:

Is there a plan or commitment for Python to implement at least "default
word boundaries" (a Level 2 feature), rather than the current "simple
word boundaries"?  I don't believe that the algorithm for this is a
whole lot more complicated, but it certainly makes a huge difference for
processing non-Roman text.

For example, to match the whole word રત without matching the word રતા
(which has an additional vowel at the end, the vertical line), with
"default word boundary" recognition, you could use the pattern \bરત\b. 
With Python's current "simple word boundary" recognition, however, the
\b assertion is pretty much useless here, and I have yet to see a decent
zero-width pattern that can take its place.

BTW, the ICU regex libraries do provide this level of Unicode support:
It seems to work perfectly on Indic text, based on the tests I've done.

Being open-source, it may be a helpful reference for the algorithm needed.

msg94857 - (view) Author: Martin v. Löwis (loewis) * (Python committer) Date: 2009-11-03 06:12
> Is there a plan or commitment for Python to implement at least "default
> word boundaries" (a Level 2 feature), rather than the current "simple
> word boundaries"?

No such plan exists at this time. Contributions are welcome.
msg113928 - (view) Author: Matthew Barnett (mrabarnett) * (Python triager) Date: 2010-08-14 20:27
These have been added to the new 'regex' module. See issue #2636 or PyPI at:
msg113979 - (view) Author: daniel mccloy (RegEx4All) Date: 2010-08-15 17:51
Woo-HOOO!  Am very excited to hear this!  Thanks, Matthew!  This and also the related \w \W handling (#1693050) should be extremely useful for processing Indic text.  I'm a python newbie, so will need to find some help on what I need to do to compile/install/use this source-file download, but if I can figure that out, I'd be very happy to test this against a texts in a variety of Indic scripts.  Way to go!
msg113993 - (view) Author: Matthew Barnett (mrabarnett) * (Python triager) Date: 2010-08-15 18:47
If you're on Windows (x86, 32-bit) then compilation isn't necessary - just use the appropriate _regex.pyd.
msg231607 - (view) Author: Amaury Forgeot d'Arc (amaury.forgeotdarc) * (Python committer) Date: 2014-11-24 16:16
Closing this old issue: either use the 'regex' module, or wait for issue2636.
Date User Action Args
2022-04-11 14:56:54adminsetgithub: 51504
2014-11-24 16:16:58amaury.forgeotdarcsetstatus: open -> closed

nosy: + amaury.forgeotdarc
messages: + msg231607

resolution: works for me
2010-08-15 18:47:44mrabarnettsetmessages: + msg113993
2010-08-15 17:51:07RegEx4Allsetmessages: + msg113979
2010-08-14 20:27:37mrabarnettsetnosy: + mrabarnett
messages: + msg113928
2009-11-03 14:34:24ezio.melottisetpriority: normal
nosy: + ezio.melotti

versions: + Python 2.7
2009-11-03 06:12:46loewissetnosy: + loewis
messages: + msg94857
2009-11-03 04:22:02RegEx4Allcreate