sfa/util/defaultdict.py

   1 # from http://code.activestate.com/recipes/523034/
   2 try:
   3     from collections import defaultdict
   4 except:
   5     class defaultdict(dict):
   6
   7         def __init__(self, default_factory=None, *a, **kw):
   8             if (default_factory is not None and
   9                     not hasattr(default_factory, '__call__')):
  10                 raise TypeError('first argument must be callable')
  11             dict.__init__(self, *a, **kw)
  12             self.default_factory = default_factory
  13
  14         def __getitem__(self, key):
  15             try:
  16                 return dict.__getitem__(self, key)
  17             except KeyError:
  18                 return self.__missing__(key)
  19
  20         def __missing__(self, key):
  21             if self.default_factory is None:
  22                 raise KeyError(key)
  23             self[key] = value = self.default_factory()
  24             return value
  25
  26         def __reduce__(self):
  27             if self.default_factory is None:
  28                 args = tuple()
  29             else:
  30                 args = self.default_factory,
  31             return type(self), args, None, None, list(self.items())
  32
  33         def copy(self):
  34             return self.__copy__()
  35
  36         def __copy__(self):
  37             return type(self)(self.default_factory, self)
  38
  39         def __deepcopy__(self, memo):
  40             import copy
  41             return type(self)(self.default_factory,
  42                               copy.deepcopy(list(self.items())))
  43
  44         def __repr__(self):
  45             return 'defaultdict(%s, %s)' % (self.default_factory,
  46                                             dict.__repr__(self))