from collections import Iterator

class Foo(Iterator):
    def __init__(self, stop):
        self.x = 0
        self.stop = stop

    def __iter__(self):
        return self

    def next(self):
        if self.x < self.stop:
            i = self.x
            self.x += 1
            return i
        else:
            raise StopIteration

    __next__ = next     # Python 3 compatibility


foo = Foo(10)
for n in foo:
    print(n),