Class Countdown

src/4/iterating_in_reverse/example.py:3–19

# Example of an object implementing both forward and reversed iterators

class Countdown:
    def __init__(self, start):
        self.start = start

    # Forward iterator
    def __iter__(self):
        n = self.start
        while n > 0:
            yield n
            n -= 1

    # Reverse iterator
    def __reversed__(self):
        n = 1
        while n <= self.start:
            yield n
            n += 1

c = Countdown(5)
print("Forward:")