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Created on 2012年05月31日 03:04 by 猫.黒, last changed 2022年04月11日 14:57 by admin.
| Files | ||||
|---|---|---|---|---|
| File name | Uploaded | Description | Edit | |
| super_setattr.patch | daniel.urban, 2012年06月04日 19:26 | __setattr__ and __delattr__ for super | review | |
| 44560_44559.diff | torsten, 2012年08月22日 16:00 | Alternate patch, targeted at Python 2.7 | ||
| superprop.py | simonzack, 2014年12月27日 08:26 | |||
| duper.py | willrazen, 2021年05月21日 01:47 | Python workaround | ||
| Pull Requests | |||
|---|---|---|---|
| URL | Status | Linked | Edit |
| PR 26194 | open | Aaron Gallagher, 2021年05月17日 18:38 | |
| PR 29950 | open | SwooshyCueb, 2021年12月07日 04:20 | |
| Messages (21) | |||
|---|---|---|---|
| msg161980 - (view) | Author: 猫 黒 (猫.黒) | Date: 2012年05月31日 03:04 | |
super() objects allow access to inherited properties fget() but not fset() or fdel(), resulting in unexpected behavior. Today on pydev thread 'Property inheritance in Python' GvR said "I don't see the need for a Python-Ideas detour. It seems worth fixing" >>> class BaseProp(object): ... @property ... def p(self): ... return self._p ... @p.setter ... def p(self, value): ... self._p = value >>> class DerivedProp(BaseProp): ... @property ... def p(self): ... return super(DerivedProp, self).p * 2 ... @p.setter ... def p(self, value): ... super(DerivedProp, self).p = value / 2 >>> d = DerivedProp() >>> d._p = 21 >>> d.p 42 >>> d.p = 50 Traceback (most recent call last): ... AttributeError: 'super' object has no attribute 'p' |
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| msg162050 - (view) | Author: josmiley (josmiley) | Date: 2012年06月01日 05:31 | |
>>> class DerivedProp(BaseProp): ... @property ... def p(self): ... return super(DerivedProp, self).p * 2 ... @p.setter ... def p(self, value): ... BaseProp.p.__set__(self,value / 2) |
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| msg162283 - (view) | Author: Daniel Urban (daniel.urban) * (Python triager) | Date: 2012年06月04日 19:26 | |
I'm attaching a patch implementing super.__setattr__ (and __delattr__). The implementation in the patch only works, if super can find a data descriptor in the MRO, otherwise it throws an AttributeError. As it can be seen in the tests, in some cases this may result in counter-intuitive behaviour. But I wasn't able to find another behaviour, that is consistent with both super.__getattr__ and normal __setattr__ semantics. |
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| msg168895 - (view) | Author: Torsten Landschoff (torsten) * | Date: 2012年08月22日 16:00 | |
I stumbled across this omission as well in 2010 and brought this up on python-dev: http://mail.python.org/pipermail/python-dev/2010-April/099672.html There were no replies, but perhaps my post adds a bit of information and also there is another patch linked from there. I attached my patch from 2010 for reference. |
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| msg174404 - (view) | Author: Andrew Svetlov (asvetlov) * (Python committer) | Date: 2012年11月01日 12:04 | |
I'm -0 for proposed changes, these changes reduce code readability from my perspective. I think better to use existing approach: explicitly specify what do you want to do with overloaded properties. |
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| msg174863 - (view) | Author: 猫 黒 (猫.黒) | Date: 2012年11月05日 05:02 | |
I'm not a python dev, but would you say super(self.__class__, self.__class__).x.fset(self, value) is more readable than super().x = value |
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| msg174911 - (view) | Author: Andrew Svetlov (asvetlov) * (Python committer) | Date: 2012年11月05日 14:37 | |
I would say @x.deleter def x(self): del super().x confuses me a bit. But I'm only -0, let's see other developers for their opinions. |
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| msg179217 - (view) | Author: David Beazley (dabeaz) | Date: 2013年01月06日 20:20 | |
Just as a note, there is a distinct possibility that a "property" in a superclass could be some other kind of descriptor object that's not a property. To handle that case, the solution of super(self.__class__, self.__class__).x.fset(self, value) would actually have to be rewritten as super(self.__class__, self.__class__).x.__set__(self, value) That said, I agree it would be nice to have a simplified means of accomplishing this. |
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| msg232438 - (view) | Author: Simon Zack (simonzack) | Date: 2014年12月10日 18:39 | |
+1 to this feature, this will dramatically simplify property setting code. |
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| msg233127 - (view) | Author: Simon Zack (simonzack) | Date: 2014年12月27日 08:26 | |
For those who want to use this right away, I've added a python implementation of the patch, which passes the unit tests. There's a slight difference in usage, where instead of using super() directly, super_prop(super()) needs to be used, so we can still use super without arguments. |
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| msg275855 - (view) | Author: Christian Heimes (christian.heimes) * (Python committer) | Date: 2016年09月11日 21:00 | |
I had to add a workaround to ssl.SSLContext and would appreciate a better solution. |
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| msg391838 - (view) | Author: Victor Milovanov (Victor Milovanov) | Date: 2021年04月25日 05:31 | |
There's a patch attached to this bug. Why is its stage "needs patch"? |
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| msg393838 - (view) | Author: Aaron Gallagher (habnabit) | Date: 2021年05月17日 22:26 | |
@daniel.urban I'm attempting to move this patch along, but since the contributing process has changed in the years since your patch, you'll need to sign the CLA. Are you interested in picking this back up at all? I haven't been given any indication of how to proceed if I'm doing this on your behalf, but hopefully the core team will enlighten us. |
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| msg394071 - (view) | Author: Will Razen (willrazen) | Date: 2021年05月20日 21:46 | |
@simonzack Your superprop.py doesn't work for multiple inheritance, because you're using __thisclass__.__mro__ in each step instead of the initial object mro |
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| msg394074 - (view) | Author: Daniel Urban (daniel.urban) * (Python triager) | Date: 2021年05月20日 22:03 | |
@habnabit I believe I've already signed some contributor form some years ago. If there is a new one, I can sign that one too. |
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| msg394094 - (view) | Author: Will Razen (willrazen) | Date: 2021年05月21日 01:47 | |
Fixed superprop.py workaround, now works with multiple inheritance and follows mro adequately. Renamed to duper.py as inspired by Torsten. Uploading here and also to https://gist.github.com/willrazen/bef3fcb26a83dffb6692e5e10d3e67ac |
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| msg394657 - (view) | Author: Aaron Gallagher (habnabit) | Date: 2021年05月28日 13:14 | |
@daniel.urban would you kindly resubmit your patch as a PR to the cpython repo? I've learned out-of-band from someone else that putting patches on bpo is considered obsolete. you can use the PR I've submitted (https://github.com/python/cpython/pull/26194) and reset the author. I'd be happy to do it myself (giving you a branch that's all set up, so all you need to do is click the 'new PR' button) if you tell me what to set the author to. |
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| msg408070 - (view) | Author: Raymond Hettinger (rhettinger) * (Python committer) | Date: 2021年12月09日 03:06 | |
-0 from me as well. I don't think this is common or something that should be encouraged. As Andrew points out, "del super().x" doesn't have an obvious meaning and it could be regarded as a code smell. The OP's first example would be an unpleasant API to debug -- it exhibits tight coupling between the parent and child class, it has Liskov issues, and it has implicit forwarding and indirection through descriptors. The tight coupling is especially problematic because Python's super() isn't guaranteed to call the parent class; rather, it can call a sibling class as determined by the MRO which cannot be known at the time the class is written. Another thought is that super() is intentionally not a completely transparent proxy. While an explicit call super().__getitem__(k) works, we've denied support for super()[k]. To me, "super().x = 10" and "del super().x" fall in the same category. Looking at the OP's Fortunately, it doesn't seem to be a common need to use super() in a property setter or deleter to bypass the current class and call setter or deleter in a parent class property. Arguably, this kind of tight coupling isn't good design. The OP's first example would be an unpleasant API to debug. FWIW, |
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| msg408071 - (view) | Author: Raymond Hettinger (rhettinger) * (Python committer) | Date: 2021年12月09日 03:08 | |
Another thought: Given that this tracker issue has been open for a decade without resolution, we have evidence that this isn't an important problem in practice. Arguably, people have been better off being nudged in another direction toward better design or having been forced to be explicit about what method is called and when. |
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| msg408072 - (view) | Author: Aaron Gallagher (habnabit) | Date: 2021年12月09日 03:10 | |
I will note, Raymond, that I’ve wanted this for years before discovering this bpo issue, and I found it because you linked it on Twitter. ;) On Wed, Dec 8, 2021 at 19:08 Raymond Hettinger <report@bugs.python.org> wrote: > > Raymond Hettinger <raymond.hettinger@gmail.com> added the comment: > > Another thought: Given that this tracker issue has been open for a decade > without resolution, we have evidence that this isn't an important problem > in practice. > > Arguably, people have been better off being nudged in another direction > toward better design or having been forced to be explicit about what method > is called and when. > > ---------- > > _______________________________________ > Python tracker <report@bugs.python.org> > <https://bugs.python.org/issue14965> > _______________________________________ > |
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| msg408155 - (view) | Author: Ronny Pfannschmidt (Ronny.Pfannschmidt) | Date: 2021年12月09日 19:32 | |
im on the noisy list because i faced this first in 2012 a key problem where i ran into this was mixins, - depending on whether a mixin was added or not one would get errors or not from my pov a super object should look like the "next class" so properties of the next base should behave as such, special methods as well |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022年04月11日 14:57:31 | admin | set | github: 59170 |
| 2021年12月09日 19:32:05 | Ronny.Pfannschmidt | set | messages: + msg408155 |
| 2021年12月09日 03:10:46 | habnabit | set | messages: + msg408072 |
| 2021年12月09日 03:08:37 | rhettinger | set | messages: + msg408071 |
| 2021年12月09日 03:06:20 | rhettinger | set | nosy:
+ rhettinger messages: + msg408070 versions: - Python 3.9, Python 3.10 |
| 2021年12月07日 04:20:42 | SwooshyCueb | set | nosy:
+ SwooshyCueb pull_requests: + pull_request28175 |
| 2021年05月28日 13:14:49 | habnabit | set | messages: + msg394657 |
| 2021年05月21日 01:47:46 | willrazen | set | files:
+ duper.py messages: + msg394094 |
| 2021年05月20日 22:03:37 | daniel.urban | set | messages: + msg394074 |
| 2021年05月20日 21:46:53 | willrazen | set | nosy:
+ willrazen messages: + msg394071 |
| 2021年05月17日 22:26:44 | habnabit | set | nosy:
+ habnabit messages: + msg393838 |
| 2021年05月17日 18:38:58 | Aaron Gallagher | set | nosy:
+ Aaron Gallagher pull_requests: + pull_request24811 stage: needs patch -> patch review |
| 2021年05月05日 04:57:27 | wyz23x2 | set | components:
+ Interpreter Core, - Extension Modules versions: + Python 3.9, Python 3.10, Python 3.11, - Python 3.7 |
| 2021年04月25日 05:31:46 | Victor Milovanov | set | nosy:
+ Victor Milovanov messages: + msg391838 |
| 2017年03月23日 04:47:00 | Mariatta | set | versions: + Python 3.7, - Python 3.5 |
| 2017年03月20日 16:57:48 | kenodegard | set | nosy:
+ kenodegard |
| 2017年02月05日 03:59:36 | THRlWiTi | set | nosy:
+ THRlWiTi |
| 2016年09月11日 21:00:29 | christian.heimes | set | nosy:
+ christian.heimes messages: + msg275855 |
| 2016年09月11日 19:03:50 | jcasale | set | nosy:
+ jcasale |
| 2016年09月08日 20:27:41 | ethan.furman | set | nosy:
+ ethan.furman |
| 2015年02月04日 14:32:49 | piotr.dobrogost | set | nosy:
+ piotr.dobrogost |
| 2014年12月27日 08:26:39 | simonzack | set | files:
+ superprop.py messages: + msg233127 |
| 2014年12月10日 18:39:27 | simonzack | set | nosy:
+ simonzack messages: + msg232438 |
| 2014年01月31日 22:28:33 | yselivanov | set | versions: + Python 3.5, - Python 3.2, Python 3.3 |
| 2013年03月21日 20:23:49 | kynan | set | nosy:
+ kynan |
| 2013年02月24日 01:08:24 | r.david.murray | link | issue783528 superseder |
| 2013年01月06日 20:20:16 | dabeaz | set | nosy:
+ dabeaz messages: + msg179217 |
| 2012年11月05日 14:37:02 | asvetlov | set | messages: + msg174911 |
| 2012年11月05日 05:02:48 | 猫.黒 | set | messages: + msg174863 |
| 2012年11月01日 12:04:42 | asvetlov | set | nosy:
+ asvetlov messages: + msg174404 |
| 2012年10月30日 20:21:14 | Ronny.Pfannschmidt | set | nosy:
+ Ronny.Pfannschmidt |
| 2012年10月30日 13:42:37 | r.david.murray | link | issue16363 superseder |
| 2012年08月24日 08:30:38 | cvrebert | set | nosy:
+ cvrebert |
| 2012年08月22日 16:00:02 | torsten | set | files:
+ 44560_44559.diff nosy: + torsten messages: + msg168895 |
| 2012年06月04日 19:27:15 | daniel.urban | set | components: + Extension Modules, - Library (Lib) |
| 2012年06月04日 19:26:52 | daniel.urban | set | files:
+ super_setattr.patch nosy: + daniel.urban messages: + msg162283 keywords: + patch |
| 2012年06月02日 05:04:28 | ncoghlan | set | nosy:
+ ncoghlan |
| 2012年06月01日 05:31:41 | josmiley | set | nosy:
+ josmiley messages: + msg162050 |
| 2012年06月01日 02:53:22 | eric.araujo | set | nosy:
+ eric.araujo stage: needs patch versions: + Python 3.3 |
| 2012年05月31日 03:07:08 | alex | set | nosy:
+ alex |
| 2012年05月31日 03:04:01 | 猫.黒 | create | |