Counting letter occurances Python

Question

I am trying to count letter occurances and print them. This is what i have so far:

def histogram(L):
    d = {}
    for x in L:
      for letter in x:
               


        

Answer 1

d is a dictionary, not a list. Loop over the keys:

for key in d:
    print('{} | {}'.format(key, d[key]))

or you'll get KeyError exceptions.

You may be interested in the collections.Counter() class; it's a counting dictionary:

from collections import Counter

def histogram(L):
    d = Counter(letter for line in L for letter in x)
    for letter in d:
        print('{} | {}'.format(letter, d[letter]))
    return d

Answer 2

Just for fun, lets simplify your code. You can use a set() on the initial string to get a list of the unique characters, then just use the count method of the list.

def histogram(L):
    d = {letter:L.count(letter) for letter in set(L)}
    for key in d:
        print "{} | {}".format(key, d[key]}