Sort Python dictionary

August 26th, 2008

Suppose that mydict is a dictionary defined by

1	mydict = {'a': 2, 'c': 5, 'b': 1, 'd': 4}

Remember that dictionary has no function sort, since it is unordered, not like a list, or tuple.

However, the key function, introduced in version 2.4, is helpful in sorting a dictionary.

To sort by items, and return the keys and items,

1	sorted( mydict.items(), key=lambda x: x[1] )

output:

[('b', 1), ('a', 2), ('d', 4), ('c', 5)]

To return only the keys, sorted by the items,

1	sorted( mydict.keys(), key=lambda x: mydict[x] )

output:

['b', 'a', 'd', 'c']

Note that, adding reverse=True at the end of the sorted function would produce a decending order list.

sorted( mydict.items(), key=lambda x: x[1] )

output:

[('c', 5), ('d', 4), ('a', 2), ('b', 1)]

Happy sorting.

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