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"""Key functions for memoizing decorators.""" |
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__all__ = ("hashkey", "methodkey", "typedkey") |
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class _HashedTuple(tuple): |
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"""A tuple that ensures that hash() will be called no more than once |
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per element, since cache decorators will hash the key multiple |
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times on a cache miss. See also _HashedSeq in the standard |
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library functools implementation. |
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""" |
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__hashvalue = None |
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def __hash__(self, hash=tuple.__hash__): |
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hashvalue = self.__hashvalue |
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if hashvalue is None: |
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self.__hashvalue = hashvalue = hash(self) |
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return hashvalue |
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def __add__(self, other, add=tuple.__add__): |
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return _HashedTuple(add(self, other)) |
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def __radd__(self, other, add=tuple.__add__): |
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return _HashedTuple(add(other, self)) |
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def __getstate__(self): |
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return {} |
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_kwmark = (_HashedTuple,) |
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def hashkey(*args, **kwargs): |
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"""Return a cache key for the specified hashable arguments.""" |
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if kwargs: |
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return _HashedTuple(args + sum(sorted(kwargs.items()), _kwmark)) |
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else: |
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return _HashedTuple(args) |
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def methodkey(self, *args, **kwargs): |
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"""Return a cache key for use with cached methods.""" |
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return hashkey(*args, **kwargs) |
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def typedkey(*args, **kwargs): |
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"""Return a typed cache key for the specified hashable arguments.""" |
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key = hashkey(*args, **kwargs) |
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key += tuple(type(v) for v in args) |
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key += tuple(type(v) for _, v in sorted(kwargs.items())) |
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return key |
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