[ python-Bugs-1212411 ] Incorrect result for regular expression - "|(hello)|(world)"

[SourceForge.net]

Bugs item #1212411, was opened at 2005-06-01 05:13
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1212411&group_id=5470

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: Regular Expressions
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Vijay Kumar (karamana)
Assigned to: Gustavo Niemeyer (niemeyer)
Summary: Incorrect result for regular expression - "|(hello)|(world)"

Initial Comment:
The regular expression "|hello|world" incorrectly gives a 
match, owing to the starting '|'.  Below is a sample 
program which highlights this.  The correct result 
behavior is to return None:

If the leading '|' is removed then the result is correct.

-----
import re
m = re.search("|hello|world","This is a simple sentence")
print m

m2 = re.search("hello|world","This is a simple sentence")
print m2

---- output ---
<_sre.SRE_Match object at 0x00B71F70>
None
----------
The first one is incorrect.  Should have returned a None.


----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1212411&group_id=5470