84 lines
2.4 KiB
Python
84 lines
2.4 KiB
Python
"""Misc dict tools."""
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__all__ = ["hashdict"]
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# https://stackoverflow.com/questions/1151658/python-hashable-dicts
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class hashdict(dict):
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"""
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hashable dict implementation, suitable for use as a key into
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other dicts.
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>>> h1 = hashdict({"apples": 1, "bananas":2})
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>>> h2 = hashdict({"bananas": 3, "mangoes": 5})
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>>> h1+h2
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hashdict(apples=1, bananas=3, mangoes=5)
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>>> d1 = {}
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>>> d1[h1] = "salad"
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>>> d1[h1]
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'salad'
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>>> d1[h2]
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Traceback (most recent call last):
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...
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KeyError: hashdict(bananas=3, mangoes=5)
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based on answers from
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http://stackoverflow.com/questions/1151658/python-hashable-dicts
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"""
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def __key(self):
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return tuple(sorted(self.items()))
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def __repr__(self):
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return "{0}({1})".format(
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self.__class__.__name__,
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", ".join("{0}={1}".format(str(i[0]), repr(i[1])) for i in self.__key()),
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)
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def __hash__(self):
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return hash(self.__key())
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def __setitem__(self, key, value):
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raise TypeError(
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"{0} does not support item assignment".format(self.__class__.__name__)
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)
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def __delitem__(self, key):
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raise TypeError(
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"{0} does not support item assignment".format(self.__class__.__name__)
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)
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def clear(self):
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raise TypeError(
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"{0} does not support item assignment".format(self.__class__.__name__)
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)
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def pop(self, *args, **kwargs):
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raise TypeError(
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"{0} does not support item assignment".format(self.__class__.__name__)
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)
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def popitem(self, *args, **kwargs):
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raise TypeError(
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"{0} does not support item assignment".format(self.__class__.__name__)
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)
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def setdefault(self, *args, **kwargs):
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raise TypeError(
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"{0} does not support item assignment".format(self.__class__.__name__)
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)
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def update(self, *args, **kwargs):
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raise TypeError(
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"{0} does not support item assignment".format(self.__class__.__name__)
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)
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# update is not ok because it mutates the object
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# __add__ is ok because it creates a new object
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# while the new object is under construction, it's ok to mutate it
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def __add__(self, right):
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result = hashdict(self)
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dict.update(result, right)
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return result
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