• counter
  • string
  • dict

The simplest way of counting the occurences of a character in a string is to use collections.Counter.

from collections import Counter

s = 'Look at my string, my string is amazing, give it a lick, it tastes of pixels.'

counter = Counter(s)

print(counter.most_common(5))
# [(' ', 15), ('i', 9), ('t', 7), ('s', 6), ('a', 5)]