Are you looking for collections.Counter?
>>> import collections
>>> print(collections.Counter("Monkey"))
Counter({'M': 1, 'y': 1, 'k': 1, 'o': 1, 'n': 1, 'e': 1})
>>> print(collections.Counter("Tree"))
Counter({'e': 2, 'T': 1, 'r': 1})
>>> c = collections.Counter("Tree")
>>> print("The word 'Tree' has {} distinct letters".format(len(c)))
The word 'Tree' has 3 distinct letters
>>> print("The word 'Tree' has {} instances of the letter 'e'".format(c['e']))
The word 'Tree' has 2 instances of the letter 'e'
