Reversing the order of key-value pairs in a dictionary (Python) [duplicate]

Question

How do I reverse the order of key-value pairs of a dictionary, in Python? For example, I have this dictionary:

{"a":1, "b":2, "c":3}

I want to reverse it so that it returns:

{"c":3, "b":2, "a":1}

Is there a function that I haven't heard about that can do this? Some lines of code is fine as well.

Answer 1

Dictionary does not have any sense of order , so your key/value pairs are not ordered in any format.

If you want to preserve the order of the keys, you should use collections.OrderedDict from the start, instead of using normal dictionary , Example -

>>> from collections import OrderedDict
>>> d = OrderedDict([('a',1),('b',2),('c',3)])
>>> d
OrderedDict([('a', 1), ('b', 2), ('c', 3)])

OrderedDict would preserve the order in which the keys were entered into the dictionary. In above case, it would be the order in which the keys existed in the list - [('a',1),('b',2),('c',3)] - 'a' -> 'b' -> 'c'

Then you can get the reversed order of keys using reversed(d) , Example -

>>> dreversed = OrderedDict()
>>> for k in reversed(d):
...     dreversed[k] = d[k]
...
>>> dreversed
OrderedDict([('c', 3), ('b', 2), ('a', 1)])