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Created on 2021-09-24 13:25 by daitakahashi, last changed 2022-04-11 14:59 by admin.
| Files | ||||
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| File name | Uploaded | Description | Edit | |
| test_protocol_property.py | daitakahashi, 2021-09-24 13:25 | testcases | ||
| Messages (2) | |||
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| msg402562 - (view) | Author: Daisuke Takahashi (daitakahashi) | Date: 2021-09-24 13:25 | |
Because __instancecheck__ of _ProtocolMeta uses hasattr() and getattr(), both of which evaluate property attributes, calling isinstance() with an object and a class that inherits typing.Protocol evaluates the input object's properties in some cases.
The attached testcases include three cases of checking subtype relationship of an instance (having a property "x" that may raise RuntimeError on evaluation) and following three protocol classes;
(1) a protocol class having "x" as a property,
(2) a protocol class having "x" as a data attribute, and
(3) a protocol class having "x" as a class property that raises
RuntimeError on evaluation (>= python 3.9 only).
Expected behavior:
1. The isinstance(obj, Protocol_class) does not evaluate anything but just checks existence of attribute names.
2. All cases in the attached testcases run without any error
Thank you very much in advance.
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| msg402567 - (view) | Author: Alex Waygood (AlexWaygood) *  |
Date: 2021-09-24 14:52 | |
Related: https://bugs.python.org/issue44904 |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:59:50 | admin | set | github: 89445 |
| 2021-09-24 14:52:18 | AlexWaygood | set | nosy:
+ AlexWaygood messages: + msg402567 |
| 2021-09-24 13:25:14 | daitakahashi | create | |
