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Created on 2011-03-21 22:13 by Chris.Colbert, last changed 2022-04-11 14:57 by admin. This issue is now closed.
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| msg131691 - (view) | Author: Chris Colbert (Chris.Colbert) | Date: 2011-03-21 22:13 | |
The cmp_to_key func acts as a class factory for generating key objects that behave according to a user defined cmp function.
Many patterns/libs that make use of key functions (for example blist and the SortedCollection recipe) store the the results of the key function internally to provide faster subsequent operations. For large datasets, the number of key objects can become large, and it makes sense to keep their memory footprint as small as possible.
From this stance, I propose to add "__slots__ = ('obj',)" to the class definition of "K" in cmp_to_key to prevent the creation of the un-needed instance dict and save the memory.
I find it hard to conjure up a case where a user would need to weakref or add attributes to the return value of a key func. But should that need arise, that functionality could be provided as optional kwargs to cmp_to_key, or just have the user subclass the return value of cmp_to_key. Alternatively, the addition of __slots__ could be specified as a kwarg to cmp_to_key.
I'd be happy to make a patch for any of these (or alternative) options.
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| msg131712 - (view) | Author: Raymond Hettinger (rhettinger) *  |
Date: 2011-03-22 00:25 | |
I think this is a good idea. Am not sure whether it should be backported though. |
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| msg131713 - (view) | Author: Éric Araujo (eric.araujo) * |
Date: 2011-03-22 00:37 | |
Right, I edited the versions field to match the versions that contain cmp_to_key, but if this behavior change is just for performance, it’s not a candidate for backport. Chris: I’d go with the simpler implementation. |
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| msg131714 - (view) | Author: Roundup Robot (python-dev)  |
Date: 2011-03-22 00:54 | |
New changeset 97799a54728e by Raymond Hettinger in branch '3.2': Issue #11628: cmp_to_key should use __slots__. http://hg.python.org/cpython/rev/97799a54728e New changeset 2e5e5d515c09 by Raymond Hettinger in branch 'default': Issue #11628: cmp_to_key should use __slots__. http://hg.python.org/cpython/rev/2e5e5d515c09 |
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| msg131715 - (view) | Author: Chris Colbert (Chris.Colbert) | Date: 2011-03-22 00:59 | |
Man, you guys are quick! Cheers! |
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| msg131775 - (view) | Author: Roundup Robot (python-dev) |
Date: 2011-03-22 20:21 | |
New changeset 136298326897 by Raymond Hettinger in branch '2.7': Issue #11628: cmp_to_key should use__slots__. http://hg.python.org/cpython/rev/136298326897 |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:57:15 | admin | set | github: 55837 |
| 2011-03-22 20:21:08 | python-dev | set | nosy:
rhettinger, ncoghlan, stutzbach, eric.araujo, python-dev, Chris.Colbert messages: + msg131775 |
| 2011-03-22 00:59:33 | Chris.Colbert | set | nosy:
rhettinger, ncoghlan, stutzbach, eric.araujo, python-dev, Chris.Colbert messages: + msg131715 |
| 2011-03-22 00:55:16 | rhettinger | set | status: open -> closed nosy: rhettinger, ncoghlan, stutzbach, eric.araujo, python-dev, Chris.Colbert resolution: fixed |
| 2011-03-22 00:54:35 | python-dev | set | nosy:
+ python-dev messages: + msg131714 |
| 2011-03-22 00:37:40 | eric.araujo | set | nosy:
rhettinger, ncoghlan, stutzbach, eric.araujo, Chris.Colbert messages: + msg131713 versions: - Python 2.7, Python 3.2 |
| 2011-03-22 00:25:04 | rhettinger | set | assignee: rhettinger messages: + msg131712 nosy: rhettinger, ncoghlan, stutzbach, eric.araujo, Chris.Colbert |
| 2011-03-21 23:17:40 | eric.araujo | set | nosy:
+ eric.araujo versions: - Python 3.1, Python 3.4 |
| 2011-03-21 22:44:11 | stutzbach | set | nosy:
+ stutzbach |
| 2011-03-21 22:13:29 | Chris.Colbert | create | |