Randolf Scholz <randolf.sch...@gmail.com> added the comment:
@Terry I think the problem boils down to the fact that `@classmethod @property`
decorated methods end up not being real properties.
Calling `MyBaseClass.__dict__` reveals:
```python
mappingproxy({'__module__': '__main__',
'expensive_class_property': <classmethod at 0x7f893e95dd60>,
'expensive_instance_property': <property at 0x7f893e8a5860>,
'__dict__': <attribute '__dict__' of 'MyBaseClass' objects>,
'__weakref__': <attribute '__weakref__' of 'MyBaseClass' objects>,
'__doc__': None,
'__abstractmethods__': frozenset(),
'_abc_impl': <_abc._abc_data at 0x7f893fb98740>})
```
Two main issues:
1. Any analytics or documentation tool that has special treatment for
properties may not identify 'expensive_class_property' as a property if they
simply check via `isinstance(func, property)`. Of course, this could be fixed
by the tool-makers by doing a conditional check:
```python
isinstance(func, property) or (`isinstance(func, classmethod)` and
`isinstance(func.__func__, property)`
```
2. `expensive_class_property` does not implement `getter`, `setter`, `deleter`.
This seems to be the real dealbreaker, for example, if we do
```python
MyBaseClass.expensive_class_property = 2
MyBaseClass().expensive_instance_property = 2
```
Then the first line erroneously executes, such that
MyBaseClass.__dict__['expensive_class_property'] is now `int` instead of
`classmethod`, while the second line correctly raises `AttributeError: can't
set attribute` since the setter method is not implemented.
----------
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue45356>
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