What are Iterables and Iterators in Python

Breaking the ‘iterating confusion’ around these terms.

Photo by Matt Seymour on Unsplash

While writing an article about Generators, I realized that though iteration, iterable and iterator are so commonly used in programming; there is a certain degree of confusion around them. It’s crucial to understand the underlying concept for a better implementation. This is going to be a short and quick article to help us determine what is an iterable and what is an iterator.

Iteration

• In layman’s language it is ‘repeating steps’.
• Iteration in programming is a repetition of a block of code for a certain number of times.
• This can be achieved by using loops.

Iterable

• Iterable is an object which can be looped over or iterated over.
  e.g. List, Tuple, Set, Dictionary, File.
• In simpler words, iterable is a container which has data or values and we perform iteration over it to get elements one by one. (Can traverse through these values one by one)
• Iterable has an in-built dunder method __iter__. A simpler way to determine whether an object is iterable is to check if it supports __iter__. How? Using dir( ), it returns the list of attributes and methods supported by an object.

Iterator

• Iterator is an iterable object with a state so it remembers where it is during iteration.
  e.g. Generator
• Iterator performs the iteration to access the elements of the iterable one by one. As it maintains the internal state of elements, iterator knows how to get the next value.
• Iterators can only move forward using __next__ . It cannot go back or cannot be reset.
• Iterator supports in-built dunder methods __iter__ and __next__.

Let’s try to make sense out of all these. Say, I have 10 chips in my ‘Can of Pringles’. Taking out chips one by one several times can be referred as iteration.

Source: Yahoo