counter.py is a counter iterator that counts a number. gen_counter.py is counter which is implemented with a generator

counter.py

class Counter(object):

    """a counter iterator that counts a number
    when you invoke the (next) method"""

    def __init__(self):
        self.count = 0

    def __iter__(self):
        return self

    def next(self):
        self.count += 1
        return self.count


def main():
    count = Counter()
    print next(count)  # > 1
    print next(count)  # > 2
    print "\n iteration starts \n"
    for i in count:
        print i
        if i == 10:break


if __name__ == '__main__':
    main()

gen_counter.py

class Counter(object):

    """a counter iterator that counts a number
    when you invoke the (iter) method which generates a generator"""

    def __init__(self):
        self.count = 0

    def __iter__(self):
        while True:
            self.count += 1
            yield self.count


def main():
    count = Counter()
    print "\n iteration starts \n"
    for i in count:
        print i
        if i == 10:break


if __name__ == '__main__':
    main()