orddicts.py

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from collections import OrderedDict, Callable
 
 
class DefaultOrderedDict(OrderedDict):
    # Source: http://stackoverflow.com/a/6190500/562769
    def __init__(self, default_factory=None, *a, **kw):
        if (default_factory is not None and not isinstance(default_factory, Callable)):
            raise TypeError('first argument must be callable')
        OrderedDict.__init__(self, *a, **kw)
        self.default_factorydefault_factory = default_factory
 
    def __getitem__(self, key):
        try:
            return OrderedDict.__getitem__(self, key)
        except KeyError:
            return self.__missing____missing__(key)
 
    def __missing__(self, key):
        if self.default_factorydefault_factory is None:
            raise KeyError(key)
        self[key] = value = self.default_factorydefault_factory()
        return value
 
    def __reduce__(self):
        if self.default_factorydefault_factory is None:
            args = tuple()
        else:
            args = self.default_factorydefault_factory,
        return type(self), args, None, None, self.items()
 
    def copy(self):
        return self.__copy____copy__()
 
    def __copy__(self):
        return type(self)(self.default_factorydefault_factory, self)
 
    def __deepcopy__(self, memo):
        import copy
        return type(self)(self.default_factorydefault_factory,
                          copy.deepcopy(self.items()))
 
    def __repr__(self):
        return 'OrderedDefaultDict(%s, %s)' % (self.default_factorydefault_factory,
                                               OrderedDict.__repr__(self))