OrderedDict可以保持插入时的顺序，上示例：

from collections import OrderedDict


d = OrderedDict()
d['foo'] = 1
d['bar'] = 2
d['spam'] = 3
d['grok'] = 4
# Outputs "foo 1", "bar 2", "spam 3", "grok 4"
for key in d:
    print(key, d[key])

输出：

python之OrderedDict_Python