Most Efficient way to calculate Frequency of values in a Python list?
Python2.7+
>>> from collections import Counter>>> L=['a','b','a','b']>>> print(Counter(L))Counter({'a': 2, 'b': 2})>>> print(Counter(L).items())dict_items([('a', 2), ('b', 2)])python2.5/2.6
>>> from collections import defaultdict>>> L=['a','b','a','b']>>> d=defaultdict(int)>>> for item in L:>>> d[item]+=1>>> >>> print ddefaultdict(<type 'int'>, {'a': 2, 'b': 2})>>> print d.items()[('a', 2), ('b', 2)]