try: from collections import defaultdict except: class defaultdict(dict): def __init__(self, default_factory=None, *a, **kw): if (default_factory is not None and not hasattr(default_factory, '__call__')): raise TypeError('first argument must be callable') dict.__init__(self, *a, **kw) self.default_factory = default_factory def __getitem__(self, key): try: return dict.__getitem__(self, key) except KeyError: return self.__missing__(key) def __missing__(self, key): if self.default_factory is None: raise KeyError(key) self[key] = value = self.default_factory() return value def __reduce__(self): if self.default_factory is None: args = tuple() else: args = self.default_factory, return type(self), args, None, None, self.items() def copy(self): return self.__copy__() def __copy__(self): return type(self)(self.default_factory, self) def __deepcopy__(self, memo): import copy return type(self)(self.default_factory, copy.deepcopy(self.items())) def __repr__(self): return 'defaultdict(%s, %s)' % (self.default_factory, dict.__repr__(self))