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# Dictionaries
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import itertools
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import UserDict
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def is_dict(value): return hasattr(value, 'keys')
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class DictProxy(UserDict.DictMixin):
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'''A proxy that forwards all accesses to an inner dict.'''
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def __init__(self, inner=None):
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if inner == None: inner = {}
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self.inner = inner
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def keys(self): return self.inner.keys()
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def __getitem__(self, key): return self.inner[key]
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def __setitem__(self, key, value): self.inner[key] = value
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class KeyExistsError(KeyError):
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def __init__(self, key):
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KeyError.__init__(self, key)
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self.key = key
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class OnceOnlyDict(DictProxy):
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'''A dict that only allows each key to be assigned once (no overwriting).'''
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def __setitem__(self, key, value):
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if key in self.inner: raise KeyExistsError(key)
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DictProxy.__setitem__(self, key, value)
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class IdCompared:
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'''A value that's compared using `is` instead of ==.
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Do not use this for strings as they are interned, causing `is` to have the
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same meaning as ==.
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'''
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def __init__(self, value): self.value = value
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def __eq__(self, other):
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return (other != None and other.__class__ == self.__class__
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and other.value is self.value)
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def __hash__(self): return id(self.value)
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class IdDict(dict):
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'''A dict that stores objects by id()'''
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def add(self, *values):
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for value in values: self[id(value)] = value
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return self
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def add_vars(self, vars_): return self.add(*vars_.values())
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class MergeDict:
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'''A dict that checks each of several dicts'''
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def __init__(self, *dicts): self.dicts = dicts
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def __getitem__(self, key):
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for dict_ in self.dicts:
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try: return dict_[key]
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except KeyError: pass
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raise # reraise last KeyError
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class AttrsDictView:
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'''A dict view of an object's attributes
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@pre If you want __iter__() to work, value must have a __dict__
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'''
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def __init__(self, value): self.value = value
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def __iter__(self): return iter(self.value.__dict__)
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def __getitem__(self, key): return getattr(self.value, key)
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import util
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def make_hashable(value):
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if isinstance(value, list): value = tuple(value)
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elif isinstance(value, dict): value = util.NamedTuple(**value)
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return value
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def join(dict0, dict1):
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'''Joins dict0 (A->B mapping) to dict1 (B->C mapping) SQL-style.
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If a value in dict0 has no key in dict1, uses the value itself.
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'''
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new_dict = {}
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for out, in_ in dict0.iteritems():
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try: out_value = dict1.get(in_, in_) # use in_ if no match found
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except TypeError: out_value = in_ # unhashable type
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new_dict[out] = out_value
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return new_dict
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