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- """Key functions for memoizing decorators."""
- __all__ = ("hashkey", "methodkey", "typedkey")
- class _HashedTuple(tuple):
- """A tuple that ensures that hash() will be called no more than once
- per element, since cache decorators will hash the key multiple
- times on a cache miss. See also _HashedSeq in the standard
- library functools implementation.
- """
- __hashvalue = None
- def __hash__(self, hash=tuple.__hash__):
- hashvalue = self.__hashvalue
- if hashvalue is None:
- self.__hashvalue = hashvalue = hash(self)
- return hashvalue
- def __add__(self, other, add=tuple.__add__):
- return _HashedTuple(add(self, other))
- def __radd__(self, other, add=tuple.__add__):
- return _HashedTuple(add(other, self))
- def __getstate__(self):
- return {}
- # used for separating keyword arguments; we do not use an object
- # instance here so identity is preserved when pickling/unpickling
- _kwmark = (_HashedTuple,)
- def hashkey(*args, **kwargs):
- """Return a cache key for the specified hashable arguments."""
- if kwargs:
- return _HashedTuple(args + sum(sorted(kwargs.items()), _kwmark))
- else:
- return _HashedTuple(args)
- def methodkey(self, *args, **kwargs):
- """Return a cache key for use with cached methods."""
- return hashkey(*args, **kwargs)
- def typedkey(*args, **kwargs):
- """Return a typed cache key for the specified hashable arguments."""
- key = hashkey(*args, **kwargs)
- key += tuple(type(v) for v in args)
- key += tuple(type(v) for _, v in sorted(kwargs.items()))
- return key
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