[issue19055] Regular expressions: * does not match as many repetitions as possible.
Jason Stumpf added the comment: I like that clearer description. as produce matches is more correct than as possible. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue19055 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue19055] Regular expressions: * does not match as many repetitions as possible.
New submission from Jason Stumpf:
re.match('(a|ab)*',('aba')).group(0)
'a'
According to the documentation, the * should match as many repetitions as
possible. 2 are possible, it matches 1.
Reversing the order of the operands of | changes the behaviour.
re.match('(ab|a)*',('aba')).group(0)
'aba'
--
messages: 198116
nosy: Jason.Stumpf
priority: normal
severity: normal
status: open
title: Regular expressions: * does not match as many repetitions as possible.
type: behavior
versions: Python 2.7
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[issue19055] Regular expressions: * does not match as many repetitions as possible.
Changes by Jason Stumpf jstu...@google.com: -- components: +Regular Expressions nosy: +ezio.melotti, mrabarnett ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue19055 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue19055] Regular expressions: * does not match as many repetitions as possible.
Jason Stumpf added the comment:
Even with the documentation to |, the documentation to * is wrong.
re.match('(a|ab)*c',('abac')).group(0)
'abac'
From the doc: In general, if a string p matches A and another string q matches
B, the string pq will match AB.
Since '(a|ab)*c' matches 'abac', and 'c' matches 'c', that means '(a|ab)*'
matches 'aba'. It does so with 2 repetitions. Thus, in the example from my
initial post, it was not matching with as many repetitions as possible.
I think what you mean is that * attempts to match again after each match of the
preceding regular expression.
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[issue19055] Regular expressions: * does not match as many repetitions as possible.
Jason Stumpf added the comment: Sorry, that implication was backwards. I don't think I can prove from just the documentation that '(a|ab)*' can match 'aba' in certain contexts. If the docs said: * attempts to match again after each match of the preceding regular expression. I think it would describe the observed behaviour. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue19055 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue19055] Regular expressions: * does not match as many repetitions as possible.
Jason Stumpf added the comment: I understand what's happening, but that is not what the documentation describes. If the behaviour is correct, the documentation is incorrect. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue19055 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
