How can I create custom iterators in Python?

How can I create custom iterators in Python?

You can create custom iterators in Python by defining a class with the __iter__() and __next__() methods.

Can you show me a simple example of a custom iterator?

Sure! Here's a basic example:

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

    def __iter__(self):
        return self

    def __next__(self):
        if self.current <= 0:
            raise StopIteration
        else:
            self.current -= 1
            return self.current + 1

This iterator counts down from a specified start value.

What happens if I forget to implement __iter__?

If you forget to implement __iter__, your class won't be recognized as an iterator, and you'll get a TypeError when trying to use it in a loop.