example.py

def two(path):
    tmp = {}
    with open(path) as f:
        for line in f:
            k, v = line.split(',')
            k = k.strip()
            v = float(v)
            s, c = tmp.get(k, (0, 0))
            tmp[k] = (s+v, c+1)
    for k, (s, c) in tmp.items():
        yield k, s, s/c