Matt O'Brien Matt O'Brien - 2 months ago 6
Python Question

Summing the contents of two collections.Counter() objects

I am working with

collections.Counter()
counters. I would like to combine two of them in a meaningful manner.

Suppose I have 2 counters, say,

Counter({'menu': 20, 'good': 15, 'happy': 10, 'bar': 5})


and

Counter({'menu': 1, 'good': 1, 'bar': 3})


I am trying to end up with:

Counter({'menu': 21, 'good': 16, 'happy': 10,'bar': 8})


How can I do this?

Answer

All you need to do is add them:

>>> from collections import Counter
>>> a = Counter({'menu': 20, 'good': 15, 'happy': 10, 'bar': 5})
>>> b = Counter({'menu': 1, 'good': 1, 'bar': 3})
>>> a + b
Counter({'menu': 21, 'good': 16, 'happy': 10, 'bar': 8})

From the docs:

Several mathematical operations are provided for combining Counter objects to produce multisets (counters that have counts greater than zero). Addition and subtraction combine counters by adding or subtracting the counts of corresponding elements.