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Created on 2005-09-21 03:09 by vstinner, last changed 2022-04-11 14:56 by admin. This issue is now closed.
| Files | ||||
|---|---|---|---|---|
| File name | Uploaded | Description | Edit | |
| bug2.py | vstinner, 2005-09-21 03:09 | Test file (bug2.py) | ||
| bug.c | vstinner, 2005-09-21 03:12 | Test file in C language | ||
| Messages (6) | |||
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| msg26345 - (view) | Author: STINNER Victor (vstinner) *  |
Date: 2005-09-21 03:09 | |
Hi, I don't know if it's a bug or a feature, but Python looks very slow to process the regex ^(.+|D)*A$ for string like "xxxxxxB" (add x to run python slower). I found this bug when a try to match strings like "abc" or "a\"b" or "\"abc" or "" with the regex: >>\"((?:[^\"]+|\\\")*)\"<<. I know that ".+*" construction in not ... optimal, but Python should optimize regex like (.+|something)*. Haypo |
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| msg26346 - (view) | Author: STINNER Victor (vstinner) * |
Date: 2005-09-21 03:12 | |
Logged In: YES user_id=365388 I try the same regex with Linux Regex library, and it looks fast (but, can I compare C with Python ?) and not "buggy". See bug.c file, and type gcc -o bug bug.c && time ./bug (I get 0.000s for user ...). Victor |
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| msg26347 - (view) | Author: STINNER Victor (vstinner) * |
Date: 2005-09-21 03:18 | |
Logged In: YES user_id=365388 The "bug" only occurs when the regex doesn't match, else it's very fast to match the string. Haypo |
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| msg26348 - (view) | Author: STINNER Victor (vstinner) * |
Date: 2005-09-21 11:24 | |
Logged In: YES user_id=365388 First fix: (a+|b)* can be replaced by (a|b)*. Other optimizations : (a|b+)* and (a+|b+) can be replaced by (a|b)*. For the case (a*|b)+ ... Wait, I'm thinking on the problem :-) Hum, looks like (?:(a|b)+)?. Im' not sure. This optimizatons should be done in compile() function. Haypo |
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| msg72846 - (view) | Author: STINNER Victor (vstinner) * |
Date: 2008-09-09 11:30 | |
It's not a bug, it's a feature. I wrote a library (http://hachoir.org/wiki/hachoir-regex) to "optimize" regex, so you can close this issue. |
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| msg72848 - (view) | Author: Antoine Pitrou (pitrou) * |
Date: 2008-09-09 11:35 | |
Fair enough :) |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:56:13 | admin | set | github: 42394 |
| 2008-09-09 11:35:35 | pitrou | set | status: open -> closed nosy: + pitrou resolution: wont fix messages: + msg72848 |
| 2008-09-09 11:30:09 | vstinner | set | messages: + msg72846 |
| 2008-04-24 21:10:58 | rsc | set | nosy: + rsc |
| 2008-01-29 12:33:34 | orivej | set | nosy: + orivej |
| 2005-09-21 03:09:18 | vstinner | create | |