Question

for i want to decode a dict to json,but i found the output order is not i desired,then i do a test like this:

a = {'a':'1st','ab':'2nd'}
print(a)
a = {'b':'1st','bc':'2nd'}
print(a)
a = {'c':'1st','cd':'2nd'}
print(a)
a = {'d':'1st','de':'2nd'}
print(a)
a = {'e':'1st','ef':'2nd'}
print(a)
a = {'f':'1st','fg':'2nd'}
print(a)

out put is

{'a': '1st', 'ab': '2nd'}
{'b': '1st', 'bc': '2nd'}
{'c': '1st', 'cd': '2nd'}
{'de': '2nd', 'd': '1st'}
{'ef': '2nd', 'e': '1st'}
{'fg': '2nd', 'f': '1st'}

because d is 100 in ascii?

how to explain it?can i change the iter order?

Answer 1

Dictionaries aren’t sorted in Python. If you want sorted dictionaries, use OrderedDict:

>>> from collections import OrderedDict
>>> a = OrderedDict((('f','1st'),('fg','2nd')))
>>> a
OrderedDict([('f', '1st'), ('fg', '2nd')])

In order to construct an OrderedDict, however, you need to use an object that preserves its sort order, like a list or a tuple.