How do I create custom iterators in Python?

How do I create custom iterators in Python?

To create a custom iterator in Python, you need to define a class with __iter__() and __next__() methods.

Can you give me an example of a custom iterator?

Sure! Here's a simple 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

How do I use this Countdown iterator?

You can use it like this:

for number in Countdown(5):
    print(number)

This will print numbers from 5 to 1.

What if I want to create an iterator that generates Fibonacci numbers?

You can create a Fibonacci iterator by modifying the __next__() method to yield Fibonacci numbers. Would you like to see that example?