Iterators and Generators

The Iterator Protocol

0:00

0% complete

LearnStep 1 of 3

Mastering the Iterator Protocol

Learning Objectives

•Implement the __iter__ and __next__ methods to create custom iterators
•Explain how StopIteration signals the end of a sequence to a for loop
•Use the iter() function with a sentinel value for alternative iteration patterns
•Differentiate between an iterable and an iterator object

Lesson Outline

LearnStep 1/3

Mastering the Iterator Protocol

In Python, iteration is powered by the Iterator Protocol. This protocol consists of two methods: __iter__ and __next__. Understanding these allows you to create efficient, memory-friendly custom sequences.

Iterables vs. Iterators

An iterable is an object capable of returning its members one at a time (e.g., lists, tuples, strings). An iterator is the object that actually performs the iteration, maintaining its own internal state.

python

Custom Iterators

To make a class an iterator, you must implement __iter__ (which typically returns self) and __next__ (which returns the next item or raises StopIteration).

python

The iter() Sentinel Pattern

The iter() function can take a second argument called a sentinel. When used this way, the first argument must be a callable. The iterator will call this callable until it returns the sentinel value.

python