json.dumps 打乱了顺序

Like the other answers correctly state, before Python 3.6, dictionaries are unordered.

That said, JSON is also supposed to have unordered mappings, so in principle it does not make much sense to store ordered dictionaries in JSON. Concretely, this means that upon reading a JSON object, the order of the returned keys can be arbitrary.

因此，在JSON中保持映射顺序(如Python OrderedDict)的一个好方法是输出一个(键、值)对数组，您可以在阅读时将其转换回有序映射:

>>> from collections import OrderedDict
>>> import json
>>> d = OrderedDict([(1, 10), (2, 20)])                                         
>>> print d[2]
20
>>> json_format = json.dumps(d.items())                   
>>> print json_format  # Order maintained
[[1, 10], [2, 20]]
>>> OrderedDict(json.loads(json_format))  # Reading from JSON: works!
OrderedDict([(1, 10), (2, 20)])
>>> _[2]  # This works!
20

(Note the way the ordered dictionary is constructed from a list of (key, value) pairs: OrderedDict({1: 10, 2: 20}) would not work: its keys are not necessarily ordered as in the dictionary literal, since the literal creates a Python dictionary whose keys are unordered.)

PS: Starting with Python 3.1, the json modules offers a hook for automatically converting a list of pairs (like above) to something else like an OrderedDict.