Message400081
The classmethod and staticmethod decorators have somewhat different semantics. Accessing a classmethod with C.cm creates a bound method object which has both __call__ and __get__. In contrast, accessing a staticmethod with C.sm returns the underlying function. So there is no opportunity for a customized __get__ method as we have with classmethod.
Also, even if C.sm did return a custom descriptor, the code example still can't be made to work because the __get__ method on property objects is hardwired to pass in an instance.¹ That means that the underlying method must have a "self" argument.
Another issue is that properties have __set__ and __delete__ methods which could not be made to work without a reference to the class or instance.
To make a read-only class variable, a metaclass would be needed. While it is possible to write a descriptor to make C.FINE_STRUCTURE_CONSTANT call a function that returns 1/137, there is no way for the descriptors to block the assignment: C.FINE_STRUCTURE_CONSTANT = 1 / 100
Thanks for the suggestion, but I don't think this can be made to work.
¹ https://docs.python.org/3/howto/descriptor.html#properties |
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Date |
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2021-08-22 17:25:36 | rhettinger | set | recipients:
+ rhettinger, tusharsadhwani |
2021-08-22 17:25:36 | rhettinger | set | messageid: <1629653136.33.0.910614959745.issue44973@roundup.psfhosted.org> |
2021-08-22 17:25:36 | rhettinger | link | issue44973 messages |
2021-08-22 17:25:36 | rhettinger | create | |
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