def histogram(s):
    d = dict()
    for c in s:
        d[c] = d.get(c, 0) + 1
    return d

print (histogram('hippopotamus'))

def histogram(s):
    d = dict()
    for c in s:
        d[c] = d.get(c, 0) + 1
    return d

print (histogram('hippopotamus'))
