In python, how do I take the highest occurrence of something in a list, and sort it that way?

Question

[3, 3, 3, 4, 4, 2]

Would be:

[ (3, 3), (4, 2), (2, 1) ]

The output should be sorted by highest count first to low

Answer 1

Why would you choose an O(n**2) algorithm to do this. The alternative to Counter (if you have <2.7) is not too difficult

>>> from operator import itemgetter
>>> from collections import defaultdict
>>> L=[3, 3, 3, 4, 4, 2]
>>> D=defaultdict(int)
>>> for i in L:
...     D[i]+=1
... 
>>> sorted(D.items(), key=itemgetter(1), reverse=True)
[(3, 3), (4, 2), (2, 1)]