How do I sort a dictionary by key?

How do I sort a dictionary by its keys?

Example input:

``````{2:3, 1:89, 4:5, 3:0}
``````

Desired output:

``````{1:89, 2:3, 3:0, 4:5}
``````

Solution

Note: for Python 3.7+, see this answer

Standard Python dictionaries are unordered (until Python 3.7). Even if you sorted the (key,value) pairs, you wouldn’t be able to store them in a `dict` in a way that would preserve the ordering.

The easiest way is to use `OrderedDict`, which remembers the order in which the elements have been inserted:

``````In [1]: import collections

In [2]: d = {2:3, 1:89, 4:5, 3:0}

In [3]: od = collections.OrderedDict(sorted(d.items()))

In [4]: od
Out[4]: OrderedDict([(1, 89), (2, 3), (3, 0), (4, 5)])
``````

Never mind the way `od` is printed out; it’ll work as expected:

``````In [11]: od[1]
Out[11]: 89

In [12]: od[3]
Out[12]: 0

In [13]: for k, v in od.iteritems(): print k, v
....:
1 89
2 3
3 0
4 5
``````

Python 3

For Python 3 users, one needs to use the `.items()` instead of `.iteritems()`:

``````In [13]: for k, v in od.items(): print(k, v)
....:
1 89
2 3
3 0
4 5
``````

Source: StackOverflow.com