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Created on 2010-11-25 16:39 by lanyjie, last changed 2022-04-11 14:57 by admin. This issue is now closed.
| Messages (3) | |||
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| msg122380 - (view) | Author: Yingjie (lanyjie) | Date: 2010-11-25 16:39 | |
Here are some puzzling results I have got (I am using Python 3, I suppose similar results for python 2).
When I do the following, I got an exception:
>>> re.findall('(d*)*', 'adb')
>>> re.findall('((d)*)*', 'adb')
When I do this, I am fine but the result is wrong:
>>> re.findall('((.d.)*)*', 'adb')
[('', 'adb'), ('', '')]
Why is it wrong?
The first mactch of groups:
('', 'adb')
indicates the outer group ((.d.)*) captured
the empty string, while the inner group (.d.)
captured 'adb', so the outer group must have
captured the empty string at the end of the
provided string 'adb'.
Once we have matched the final empty string '',
there should be no more matches, but we got
another match ('', '')!!!
So, findall matched the empty string in
the end of the string twice!!!
Isn't this a bug?
Yingjie
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| msg122384 - (view) | Author: Matthew Barnett (mrabarnett) *  |
Date: 2010-11-25 17:24 | |
The spans say this:
>>> for m in re.finditer('((.d.)*)*', 'adb'):
print(m.span())
(0, 3)
(3, 3)
There's an non-empty match followed by an empty match.
IHMO, not a bug.
|
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| msg122476 - (view) | Author: Ned Deily (ned.deily) *  |
Date: 2010-11-26 20:31 | |
Closing this issue since it appears to not be a bug. |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:57:09 | admin | set | github: 54741 |
| 2010-11-26 20:31:54 | ned.deily | set | status: open -> closed nosy: + ned.deily messages: + msg122476 resolution: not a bug |
| 2010-11-25 17:24:27 | mrabarnett | set | nosy:
+ mrabarnett messages: + msg122384 |
| 2010-11-25 16:41:06 | lanyjie | set | type: behavior |
| 2010-11-25 16:39:12 | lanyjie | create | |