Method __init__

recipes/Python/259173_Groupby/recipe-259173.py:2–5

(self, seq, key=lambda x:x)

class groupby(dict):
    def __init__(self, seq, key=lambda x:x):
        for value in seq:
            k = key(value)
            self.setdefault(k, []).append(value)
    __iter__ = dict.iteritems

# -------------------------- Examples -----------------------------------