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problem with ABCMeta.__prepare__ when called after types.new_class #77371
Description
| BPO | 33190 |
|---|---|
| Nosy | @ilevkivskyi, @Ricyteach |
| PRs | types.new_class docstring #6317 |
| Files |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = None
closed_at = None
created_at = <Date 2018-03-30.20:43:02.783>
labels = ['3.7', '3.8', 'type-bug', 'library']
title = 'problem with ABCMeta.__prepare__ when called after types.new_class'
updated_at = <Date 2018-03-31.02:58:22.949>
user = 'https://github.com/Ricyteach'bugs.python.org fields:
activity = <Date 2018-03-31.02:58:22.949>
actor = 'Ricyteach'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2018-03-30.20:43:02.783>
creator = 'Ricyteach'
dependencies = []
files = ['47509']
hgrepos = []
issue_num = 33190
keywords = ['patch']
message_count = 5.0
messages = ['314714', '314716', '314717', '314718', '314731']
nosy_count = 2.0
nosy_names = ['levkivskyi', 'Ricyteach']
pr_nums = ['6317']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue33190'
versions = ['Python 3.7', 'Python 3.8']
Activity
Ricyteach commentedon Mar 30, 2018
I am pretty sure this is a bug. If not I apologize.
Say I want to dynamically create a new
Cclass, with base classMyABC(and dynamically assigned abstract methodm). This works fine if I usetype, but if I usenew_class, the keyword argument to themmethod implementation gets lost somewhere in the call toABCMeta.__prepare___.I've attached a file to demo. Thanks.
ilevkivskyi commentedon Mar 30, 2018
This is not a bug, but a misunderstanding:
__prepare__, it is justtype.__prepare__types.new_classis calledkwdsfor a reason. It is not a namespace like intypebut the set of keywords in the equivalent class definition. For example:types.new_class('Test', (A, B), {'metaclass': Meta, 'foo': 42})
id equivalent to
If you want to populate the namespace, then you should use the fourth argument
exec_bodywhich should be a callable that takes newly created dictionary and populates it with items. For your case it should be:If you want to clarify the corresponding docstring, then please open a PR. Otherwise you can close the issue.
Ricyteach commentedon Mar 30, 2018
Excellent; thank you very much for the explanation.
I have never done a PR on a project this size but I'll give it a try.
ilevkivskyi commentedon Mar 30, 2018
https://devguide.python.org/ will help you.
Ricyteach commentedon Mar 31, 2018
Thank you; I gave it a go. Hopefully didn't cause too much additional work for someone.
furkanonder commentedon May 13, 2023
@ilevkivskyi I think we can close the problem because the issue is not a bug, it is a misunderstanding.
ilevkivskyi commentedon May 13, 2023
There is still an option to improve the docstring for
new_class()but if no-one wants to do this, then we can close.