Python OrderedDict怎么用

>>> from collections import OrderedDict

>>> d = dict([('a', 1), ('b', 2), ('c', 3)])

>>> d # dict的Key是无序的

{'a': 1, 'c': 3, 'b': 2}

>>> od = OrderedDict([('a', 1), ('b', 2), ('c', 3)])

>>> od # OrderedDict的Key是有序的

OrderedDict([('a', 1), ('b', 2), ('c', 3)])

from collections import OrderedDict

class LastUpdatedOrderedDict(OrderedDict):

    def __init__(self, capacity):

        super(LastUpdatedOrderedDict, self).__init__()

        self._capacity = capacity

    def __setitem__(self, key, value):

        containsKey = 1 if key in self else 0

        if len(self) - containsKey >= self._capacity:

            last = self.popitem(last=False)

            print('remove:', last)

        if containsKey:

            del self[key]

            print('set:', (key, value))

        else:

            print('add:', (key, value))

        OrderedDict.__setitem__(self, key, value)