def print_empty_line():
    print('')


###

class DataHolder(object):

    def __init__(self):
        self.counter = 0
        self.data = ['Hi', 'Ho', 'Foo', 'Bar']

    def __iter__(self):
        # This should return an iterator
        # In this case return self
        return self

    def __next__(self):
        if self.counter < len(self.data):
            self.counter += 1
            return self.data[self.counter - 1]
        else:
            # So we can use again
            self.counter = 0
            raise StopIteration()


###

dataholder = DataHolder()

for x in dataholder:
    print(x)

print_empty_line()
for x in dataholder:
    print(x)


###

def my_generator(n):
    # print('Begin')
    counter = 1
    while counter <= n:
        # print('Before yield')
        yield counter * counter
        # print('After yield')
        counter += 1
    # print('End')


print_empty_line()
for x in my_generator(5):
    print(x)