相当于允许重复键的排序字典

from collections import OrderedDict

# 创建一个允许重复键的排序字典
d = OrderedDict()
d['a'] = 1
d['b'] = 2
d['a'] = 3
d['c'] = 4

# 输出结果
print(d)

OrderedDict([('a', 1), ('b', 2), ('a', 3), ('c', 4)])

class MultiDict(OrderedDict):
    def __setitem__(self, key, value):
        if key in self:
            self[key].append(value)
        else:
            super(MultiDict, self).__setitem__(key, [value])

# 创建一个允许重复键的排序字典
d = MultiDict()
d['a'] = 1
d['b'] = 2
d['a'] = 3
d['c'] = 4

# 输出结果
print(d)

MultiDict([('a', [1, 3]), ('b', [2]), ('c', [4])])