Bugs item #1661745, was opened at 2007-02-16 19:11
Message generated for change (Comment added) made by gbrandl
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Category: Regular Expressions
Group: Python 2.5
>Status: Closed
>Resolution: Duplicate
Priority: 5
Private: No
Submitted By: Milan (migues)
Assigned to: Gustavo Niemeyer (niemeyer)
Summary: finditer stuck in infinite loop
Initial Comment:
Using iterator on Match Object results in infinite unbreakable loop. Attached
is sample script and sample file.
My OS: Win XP Pro.
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>Comment By: Georg Brandl (gbrandl)
Date: 2007-02-22 11:59
Message:
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Originator: NO
I'd say this is a duplicate of #1662581.
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Comment By: Adam Olsen (rhamphoryncus)
Date: 2007-02-22 10:45
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Nope, won't let me attach a file. Pasted instead:
#!/usr/bin/env python
import re
from timeit import Timer
reexpr = re.compile(r"(.+\n?)+?((\.\n)|(\n\n))")
def test(count):
text = '%s.%s.' % ('x' * count, 'x' * count)
for m in reexpr.finditer(text):
pass
for count in range(21):
print '%2i: %20.10f' % (count,
Timer('test(%i)' % count, "from __main__ import
test").timeit(number=1))
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Comment By: Adam Olsen (rhamphoryncus)
Date: 2007-02-22 10:44
Message:
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I've rewritten the test case. It's not an infinite loop but rather
exponential runtime based on the length of the string. Matching on a
string of 'x.x.', increasing the length of the left x or right x by one
doubles the runtime. Increasing both quadruples it.
0: 0.0000350475
1: 0.0000259876
2: 0.0000669956
3: 0.0002369881
4: 0.0009140968
5: 0.0038359165
6: 0.0148119926
7: 0.0732769966
8: 0.2570281029
9: 0.9819128513
10: 3.9152498245
11: 16.4304330349
12: 64.8596510887
13: 264.2261950970
I'm not a re guru though, so I don't know if this is a real bug or just
one of those special cases re is prone to.
Now I just need to find out how to attach my file, SF doesn't want to let
me..
----------------------------------------------------------------------
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