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re.match blocking and taking 100% CPU #60634

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SebastienEstienne mannequin opened this issue Nov 7, 2012 · 3 comments
Closed

re.match blocking and taking 100% CPU #60634

SebastienEstienne mannequin opened this issue Nov 7, 2012 · 3 comments
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topic-regex

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@SebastienEstienne
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SebastienEstienne mannequin commented Nov 7, 2012

BPO 16430
Nosy @mdickinson, @ezio-melotti, @serhiy-storchaka
Superseder
  • bpo-1662581: the re module can perform poorly: O(2n) versus O(n2)
    		•
    Files
  • re_bug.py: Example of the bug
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = None
closed_at = <Date 2012-11-07.17:34:32.818>
created_at = <Date 2012-11-07.17:00:35.683>
labels = ['expert-regex', 'invalid']
title = 're.match blocking and taking 100% CPU'
updated_at = <Date 2012-11-07.17:35:54.298>
user = 'https://bugs.python.org/SebastienEstienne'

    bugs.python.org fields:

    activity = <Date 2012-11-07.17:35:54.298>
actor = 'mark.dickinson'
assignee = 'none'
closed = True
closed_date = <Date 2012-11-07.17:34:32.818>
closer = 'serhiy.storchaka'
components = ['Regular Expressions']
creation = <Date 2012-11-07.17:00:35.683>
creator = 'Sebastien.Estienne'
dependencies = []
files = ['27921']
hgrepos = []
issue_num = 16430
keywords = []
message_count = 3.0
messages = ['175109', '175111', '175112']
nosy_count = 5.0
nosy_names = ['mark.dickinson', 'ezio.melotti', 'mrabarnett', 'serhiy.storchaka', 'Sebastien.Estienne']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = '1662581'
type = None
url = 'https://bugs.python.org/issue16430'
versions = ['Python 2.6', 'Python 2.7']
    @SebastienEstienne
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    SebastienEstienne mannequin commented Nov 7, 2012

    Hello

    re.match is blocked and takes 100% cpu forever

    re_bug.py is an example of the bug.

    thanx

    @SebastienEstienne SebastienEstienne mannequin added the topic-regex label Nov 7, 2012
    @serhiy-storchaka
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    There is no a Python bug.

    You have wrong regexp. Remove "$" at the end or add ".*" before "$".

    And it would be better if instead of '(?P<date>.*?)\s' and '"(?P<method_uri>.*?)"' you use '(?P<date>\S+)\s' and '"(?P<method_uri>[^"]*)"'.

    @mdickinson
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    This is a known issue: there are a good few duplicates in the tracker. Issue bpo-1662581 is one, for example.

    In this particular case, you can probably fix things by tightening up your regex. Part of the problem is that '.*' is going to match any sequence of characters, including spaces. Judicious use of '\S' to match non-whitespace characters might help. There's not much point to the '?' in '.*?', either.

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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