>>> x = dict() #无序字典
>>> x['a'] = 3
>>> x['b'] = 5
>>> x['c'] = 8
>>> x #输出并没有按输入的顺序输出
{'b': 5, 'c': 8, 'a': 3}
>>> import collections
>>> x =collections.OrderedDict() #有序字典
>>> x['a'] = 3
>>> x['b'] = 5
>>> x['c'] = 8
>>> x #输出按输入的顺序输出
OrderedDict([('a', 3), ('b', 5),('c', 8)])