[Python-Dev] Small misleadingness in docs

[Georg Brandl]

Raymond Hettinger schrieb:
> [Greg Ewing]
>> I've discovered something slightly misleading in the docs
>> for PyObject_IsInstance:
>>
>>   When testing if B is a subclass of A, if A is B, PyObject_IsSubclass
>>   returns true. If A and B are different objects, B's __bases__
>>   attribute is searched...
>>
>> This suggests that issubclass(A, A) will always be true,
>> regardless of what attributes A has. However, this turns
>> out not to be so -- A must also have a __bases__ attribute,
>> otherwise it's rejected as not being sufficiently class-like.
> 
> This smells like a bug that brings issubclass() out of sync with isinstance().
> Perhaps issubclass() should do what the docs say and start by
> testing whether A and B are the same object.

Since I cannot imagine a scenario where you would want to have non-classes
as the arguments of issubclass(), making sure that both *are* classes
sounds like a good idea to prevent bugs.

Georg

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