luccount.py

import os
import sys
from collections import Counter

if len(sys.argv) < 2:
    print('needs at least two arguments, <char set> <files>...')

characters = sys.argv[1]
counter = Counter()

for filename in sys.argv[2:]:
    with open(filename) as f:
        contents = f.read()
        for character in characters:
            counter[character] += contents.count(character)

print(counter)