Sum of all counts in a collections.Counter

Question

What is the best way of establishing the sum of all counts in a collections.Counter object?

I've tried:

sum(Counter([1,2,3,4,5,1,2,1,6]))

but this gives 21 instead of 9?

Answer 1

The code you have adds up the keys (i.e. the unique values in the list: 1+2+3+4+5+6=21).

To add up the counts, use:

In [4]: sum(Counter([1,2,3,4,5,1,2,1,6]).values())
Out[4]: 9

This idiom is mentioned in the documentation, under "Common patterns".

Answer 2

Sum the values:

sum(some_counter.values())

Demo:

>>> from collections import Counter
>>> c = Counter([1,2,3,4,5,1,2,1,6])
>>> sum(c.values())
9

Answer 3

sum(Counter([1,2,3,4,5,1,2,1,6]).values())