[Python-bugs-list] [ python-Bugs-803842 ] Wrong description of regexp concatenation

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Bugs item #803842, was opened at 2003-09-10 11:37
Message generated for change (Comment added) made by rhettinger
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Category: Documentation
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Hallvard B Furuseth (hfuru)
Assigned to: Nobody/Anonymous (nobody)
Summary: Wrong description of regexp concatenation

Initial Comment:
http://www.python.org/doc/current/lib/re-syntax.html

says:



If a string p matches A and another string q matches B,

the string pq will match AB if A and B do no specify

boundary conditions that are no longer satisfied by pq.



This is not true if A or B contains an unparenthesized

"|": A = "x|y", B = "z", p = "x", q = "z".



Nor if A contains parentheses and B contains \number.

A = "(x)", B = r'(.)\1', p = "x", q = "yy".



Nor if A or B contains a (?...) which modifies the

behaviour of the entire regular expression.



Nor if B contains (?<!...) matching AB, including

a portion of A.



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>Comment By: Raymond Hettinger (rhettinger)
Date: 2003-09-10 13:48

Message:
Logged In: YES 
user_id=80475

These two exceptions (low precedence operations and group 

numbering) seem obvious to me; however, precedence errors 

with | is are common.  Accordingly, I've updated the docs to 

the two exceptions to the general rule.



Thanks for the report.

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