What is the iterator protocol in Python?

What is the iterator protocol in Python?

The iterator protocol in Python is a set of methods that allows an object to be iterated over, typically using a for loop. It consists of two main methods: __iter__() and __next__().

Can you explain how to implement the iterator protocol in a custom class?

Sure! To implement the iterator protocol, you need to define the __iter__() method that returns the iterator object (usually self), and the __next__() method that returns the next value or raises StopIteration when there are no more values.

Could you give me a simple example of a custom iterator?

Absolutely! 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 custom iterator in a for loop?

You can use it like this:

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

This will print numbers from 5 to 1.