Simplest way to find the element that occurs the most in each column

Question

Suppose I have

data =
[[a, a, c],
 [b, c, c],
 [c, b, b],
 [b, a, c]]

I want to get a list containing the element that occurs the most in each

Answer 1

Use a list comprehension plus collections.Counter():

from collections import Counter

[Counter(col).most_common(1)[0][0] for col in zip(*data)]

zip(*data) rearranges your list of lists to become a list of columns instead. Counter() objects count how often anything appears in the input sequence, and .most_common(1) gives us the most popular element (plus it's count).

Provided your input is single character strings, that gives:

>>> [Counter(col).most_common(1)[0][0] for col in zip(*data)]
['b', 'a', 'c']