sammlung.py

# coding: utf-8

from collections import OrderedDict, Callable

# see also: http://stackoverflow.com/a/6190500/562769
class DefaultOrderedDict(OrderedDict):
    def __init__(self, default_factory=None, append_missing=True, *args, **kwargs):
        if (default_factory is not None and
           not isinstance(default_factory, Callable)):
            raise TypeError('first argument must be callable')
        OrderedDict.__init__(self, *args, **kwargs)
        self._append_missing = append_missing
        self.default_factory = default_factory

    def __getitem__(self, key):
        try:
            return OrderedDict.__getitem__(self, key)
        except KeyError:
            return self.__missing__(key)

    def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        value = self.default_factory()
        if self._append_missing:
            self[key] = value
        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 'OrderedDefaultDict(%s, %s)' % (self.default_factory,
                                               OrderedDict.__repr__(self))