On 05/07/2019 02:05 PM, Jordan Adler wrote:
Specifically, a comparison between a primitive (int, str, float were tested) and an object of a different type always return False, instead of raising a NotImplementedError. Consider `1 == '1'` as a test case.
If the object of a different type doesn't support comparing to an int, str, or float then False is the correct answer. On the other hand, if the object of a different type wants to compare equal to, say, ints then it will have to supply its own __eq__ method to return False/True as appropriate.
Should the data model be adjusted to declare that primitive types are expected to fallback to False
No, because they aren't.
or should the cpython primitive type's __eq__ implementation fallback to raise NotImplementedError?
No, because raising an error is not appropriate. Did you mean `return NotImplemented`? Because empirical evidence suggests that they do: ------- class MyCustomInt(): def __init__(self, value): self.value = value def __eq__(self, other): if isinstance(other, int): return self.value == other else: return NotImplemented def __ne__(self, other): if isinstance(other, int): return self.value != other else: return NotImplemented core_int = 7 my_int = MyCustomInt(7) print(core_int == my_int) # True print(my_int == core_int) # True ------- If the core types were not returning NotImplemented then the above would be False on the `core_int == my_int` line. Hopefully this is clearer now? -- ~Ethan~ _______________________________________________ Python-Dev mailing list [email protected] https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com