emulation of collections.defaultdict

defaultdict.py

"""
emulation of collections.defaultdict
"""
class defaultdict(dict):
    """
    emulation of collections.defaultdict

    to test, run python defaultdict.py -v

    >>> dd = defaultdict(list)
    >>> dd[1].append(2)
    >>> dd
    defaultdict(<class 'list'>, {1: [2]})

    >>> dd = defaultdict(defaultdict)
    >>> dd['a']={'key1':'value1'}
    >>> dd
    defaultdict(<class '__main__.defaultdict'>, {'a': {'key1': 'value1'}})

    >>> dd['b'].update({'key2':'value2'})
    >>> dd
    defaultdict(<class '__main__.defaultdict'>, {'a': {'key1': 'value1'}, 'b': defaultdict(None, {'key2': 'value2'})})

    >>> dd['c']['key3'] = {'key4':'value4'}
    >>> dd
    defaultdict(<class '__main__.defaultdict'>, {'a': {'key1': 'value1'}, 'b': defaultdict(None, {'key2': 'value2'}), 'c': defaultdict(None, {'key3': {'key4': 'value4'}})})

    >>> dd2 = dd.copy()
    >>> dd2
    defaultdict(<class '__main__.defaultdict'>, {'a': {'key1': 'value1'}, 'b': defaultdict(None, {'key2': 'value2'}), 'c': defaultdict(None, {'key3': {'key4': 'value4'}})})

    """

    def __init__(self, default_factory=None):
        self.default_factory = default_factory
        dict.__init__(self)

    def __repr__(self):
        # print("debug" + str(self.default_factory))
        typestr = str(self.default_factory).split("'")
        if len(typestr) == 1:
            typestr = typestr[0]
        else:
            typestr = str(self.default_factory)

        return 'defaultdict(%s, %s)' % (typestr,
                                        dict.__repr__(self))

    def __missing__(self, key):
        if self.default_factory:
            self[key] = self.default_factory()
            return self[key]
        else:
            raise KeyError(key)

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

    def copy(self):
        return self.__copy__()

    def __copy__(self):
        new = type(self)(self.default_factory)
        for key, value in self.items():
            new[key] = value
        return new


if __name__ == "__main__":
    import doctest
    doctest.testmod()

    # dd = defaultdict(list)
    # dd[1].append(2)
    # print(dd)
    # dd = defaultdict(defaultdict)
    # dd['a']={'key1':'value1'}
    # print(dd)
    # dd['b'].update({'key2':'value2'})
    # print(dd)
    # dd['c']['key3'] = {'key4':'value4'}
    # print(dd)
    # dd2 = dd.copy()
    # print(dd2)

    # from collections import defaultdict as defaultdict2
    # cdd = defaultdict(list)
    # cdd[1].append(2)
    # print(cdd)
    # cdd = defaultdict2(defaultdict2)
    # cdd['a']={'key1':'value1'}
    # print(cdd)
    # cdd['b'].update({'key2':'value2'})
    # print(cdd)
    # cdd['c']['key3'] = {'key4':'value4'}
    # print(cdd)
    # cdd2 = cdd.copy()
    # print(cdd2)