I am looking for a fast and efficient way to calculate the frequency of list items in python:
list = ['a','b','a','b', ......]
I want a frequency counter which would give me an output like this:
[ ('a', 10),('b', 8) ...]
The items should be arranged in descending order of frequency as shown above.
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 d
defaultdict(<type 'int'>, {'a': 2, 'b': 2})
>>> print d.items()
[('a', 2), ('b', 2)]
