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import collections
import operator
import functools
import sys
try:
from collections import OrderedDict
except ImportError: # python < 2.7
OrderedDict = NotImplemented
iteritems = getattr(dict, 'iteritems', dict.items) # py2-3 compatibility
class frozendict(collections.Mapping):
"""
An immutable wrapper around dictionaries that implements the complete :py:class:`collections.Mapping`
interface. It can be used as a drop-in replacement for dictionaries where immutability is desired.
"""
dict_cls = dict
def __init__(self, *args, **kwargs):
self._dict = self.dict_cls(*args, **kwargs)
self._hash = None
def __getitem__(self, key):
return self._dict[key]
def __contains__(self, key):
return key in self._dict
def copy(self, **add_or_replace):
return self.__class__(self, **add_or_replace)
def __iter__(self):
return iter(self._dict)
def __len__(self):
return len(self._dict)
def __repr__(self):
return '<%s %r>' % (self.__class__.__name__, self._dict)
def __hash__(self):
if self._hash is None:
h = 0
for key, value in iteritems(self._dict):
h ^= hash((key, value))
self._hash = h
return self._hash
class FrozenOrderedDict(frozendict):
"""
A frozendict subclass that maintains key order
"""
dict_cls = OrderedDict
if OrderedDict is NotImplemented:
del FrozenOrderedDict
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