song = """by the rivers of babylon, there we sat down
yeah we wept, when we remember zion.
when the wicked carried us away in captivity
required from us a song
now how shall we sing the lord's song in a strange land"""
alphabet = dict()
for c in song:
    if c.isalpha() == False:
        continue
    c = c.lower()
    if c not in alphabet:
        alphabet[c] = 1
    else:
        alphabet[c] += 1

print(alphabet)