Problem with SRE's regular expressions

[Christophe Delord]

Hello,

I'm using regular expressions in python in a parser generator. I have 
some troubles with the module named 're'. In fact it uses the 'sre' 
module. When I explicitly use the old 'pre' module it works fine.
So my problem is when big strings are scanned using non greedy operator 
(for example ".*?") 'sre' seems to be recursivle and python stack limit 
is exceeded. With 'pre', their is no problem. Let's consider the 
following program (I'm using Python 2.2):


import sre, pre

big_string = "<" + "that's a very very big string!"*1000 + ">"

for re in (pre, sre):
	print "testing", re
	if re.match('<.*?>', big_string):
		print "Ok, it works"
	else:
		print "Their's a problem here"


This displays :


[christ at localhost py]$ bug_re.py
testing <module 'pre' from '/usr/local/python22/lib/python2.2/pre.pyc'>
Ok, it works
testing <module 'sre' from '/usr/local/python22/lib/python2.2/sre.pyc'>
Traceback (most recent call last):
   File "./bug_re.py", line 9, in ?
     if re.match('<.*?>', big_string):
   File "/usr/local/python22/lib/python2.2/sre.py", line 132, in match
     return _compile(pattern, flags).match(string)
RuntimeError: maximum recursion limit exceeded
[christ at localhost py]$


Is this a bug in 'sre' or just a known restriction. I've tried to send a 
mail to sre's author (Fredrik Lundh) but his email address seems not to 
work. Does anyone know if this behaviour is known and if something is 
planned to correct it?

Best regards,
Christophe.


-- 
Christophe Delord
http://christophe.delord.free.fr/