How to find Run length encoding in python

Question

I have an array ar = [2,2,2,1,1,2,2,3,3,3,3]. For this array, I want to find the lengths of consecutive same numbers like:

 values: 2, 1, 2, 3
l         


        

Answer 1

You can do this with groupby

In [60]: from itertools import groupby
In [61]: ar = [2,2,2,1,1,2,2,3,3,3,3]
In [62]: print [(k, sum(1 for i in g)) for k,g in groupby(ar)]
[(2, 3), (1, 2), (2, 2), (3, 4)]