This one’s a classic! I’m a big fan of this as a warm-up question. A simple exercise of looping, strings, exercising two different cases with dictionaries (what if the key already exists, what if it’s new), and best of all it’s a pretty reasonable distillation of real programming scenarios.

def count(string):
    m = {}
    for c in string:
        if c in m:
            m[c] += 1
        else:
            m[c] = 1
    return m

I’m sure there are very fancy ways of doing this. I’d rather use a default-dictionary, but otherwise I’m happy with this solution.