问题:

from collections import OrderedDict
import pprint

menu = {"about" : "about", "login" : "login", 'signup': "signup"}

menu = OrderedDict(menu)
pprint.pprint(menu.items())

import sys
sys.exit()

The output is:

[('about', 'about'), ('signup', 'signup'), ('login', 'login')]

So, the order is not preserved even with the use of OrderedDict. I know the dictionaries don't preserve the initial order by default, and all those things. But I want to learn why the OrderedDict is not working.

回答1:

By putting the items in a (non-ordered) dict and constructing the OrderedDict from that, you've already discarded the original order. Construct the OrderedDict from a list of tuples, not a dict.

回答2:

Please find code snippet below

>>> from collections import OrderedDict
>>> listKeyVals = [(1,"One"),(2,"Two"),(3,"Three"),(4,"Four"),(5,"Five")]
>>> x = OrderedDict(listKeyVals)
>>> x
OrderedDict([(1, 'One'), (2, 'Two'), (3, 'Three'), (4, 'Four'), (5, 'Five')])
>>>

I suggest you to vist examples from my article

https://techietweak.wordpress.com/2015/11/11/python-collections/