Created
February 7, 2020 19:37
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class HasConsistentHash: | |
''' | |
A mixin to enforce that classes have hash methods that are consistent | |
with thier equality checks. | |
''' | |
def __eq__(self, other: object) -> bool: | |
''' | |
post: implies(__return__, hash(self) == hash(other)) | |
''' | |
raise NotImplementedError | |
class Apples(HasConsistentHash): | |
''' | |
Uses HasConsistentHash to discover that the __eq__ method is | |
missing a test for the `count` attribute. | |
''' | |
count: int | |
kind: str | |
def __hash__(self): | |
return self.count + hash(self.kind) | |
def __repr__(self): | |
return f'Apples({self.count!r}, {self.kind!r})' | |
def __eq__(self, other: object) -> bool: | |
return isinstance(other, Apples) and self.kind == other.kind | |
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