[New Concept Docs]: `iterators`

[BethanyG]

This issue describes how to implement the iterators concept docs. You can find the related concept exercise issue here

If you have not yet contributed to concept documents, this issue will require some upfront reading to give you the needed background knowledge.

✅ Getting started

Please please read the docs before starting. Posting PRs without reading these docs will be a lot more frustrating for you during the review cycle, and exhaust Exercism's maintainers' time.

General Contributing Docs:

• Contributing to Exercism | Exercism and GitHub | - Contributor Pull Request Guide
• What are those Weird Task Tags about?
• Exercism Formatting and Style Guide
• Exercism Markdown Specification
• Reputation

Documents on Language Tracks and Concepts:

• Building Language Tracks: An Overview
• What are Concepts?
• Concept Specifications

🎯 Goal

These concept docs are meant to teach an understanding, creation, and use of itertators in Python.

💡 Learning objectives

Learn more about how looping / iteration and the iterator protocol work in Python, and the options available for creating & customizing iterators.

• How loops in Python implement the iterator protocol
• iteration "under the covers"
• How iterables are defined
• Understand and use the built-in iter() to return an iterator
• Create/use one or more custom iterators via defining a class
• Understand how class -created iterators relate to generators, and the pros and cons of each approach

🚫 Out of scope

Concepts and Subjects that are Out of Scope

• classes & class customization beyond the use of the iterator dunder methods and iterator protocol
• class-inheritance beyond what is needed to customize iteration for a container type or other class
• comprehensions
• comprehensions in lambdas
• coroutines
• decorators
• functools and related map(), filter() and functools.reduce()
• generators in-depth as a specific form of iterators (these have their own exercise)
• higher-order functions
• lambdas
• using an assignment expression or "walrus" operator (:=)
• class decorators
• enums

🤔 Concepts

Concepts and Related Concepts this Concept Covers

• loops in Python
• iteration in Python
• iterators & iterator types
• The iterator protocol
• iterables & enumeration

↩️ Prerequisites

These are the concepts/concept exercises the student should be familiar with before taking on/learning this concept.

Prereqs

• basics
• booleans
• classes
• comparisons
• rich-comparisons
• decorators
• descriptors
• dicts
• dict-methods
• functions
• higher-order-functions
• lists
• list-methods
• numbers
• sequences
• sets
• strings
• string-methods
• tuples

📚 Resources to refer to

Resources

• Python Docs: iterator definition | Python Docs: iterator types
  • Python Docs: iterable
  • Python Tutorial: iterators | Python Functional Programming HOWTO: Iterators
  • Python Docs: sequence
  • Python Docs: the for statement
  • Trey Hunner: The Iterator Protocol: How for Loops Work in Python
  • Dan Bader: Python Iterators - A Step-by-Step Introduction
• iter()
• Python Docs: emulating container types
  • Trey Hunner: How to make an iterator in Python
  • Python Patterns Guide: Gang of Four iterator Pattern
• Python Docs C-API: Iterator Protocol
• Python Docs C-API: Iterator Objects

📁 Files to Be Created

File Detail for this Concept

Please see the following for more details on these files: concepts links.json For more information, see concept links file The same resources listed in this issue can be used as a starting point for the concepts/links.json file, if it doesn't already exist. If there are particularly good/interesting information sources for this concept that extend or supplement the concept exercise material & the resources already listed -- please add them to the links.json document. Concept about.md For more information, see Concept about.md This file provides information about this concept for a student who has completed the corresponding concept exercise. It is intended as a reference for continued learning. Concept introduction.md For more information, see Concept introduction.md This can also be a summary/paraphrase of the about.md document listed above, and will provide a brief introduction of the concept for a student who has not yet completed the associated concept or practice exercises. It should contain a good summation of the concept, but not go into lots of detail. Concept .meta/config.json Entries For more information, see Concept .meta/config.json This file is likely already stubbed out. Remember to add a concept blurb of less than 350 characters. Please also add your GitHub username to the "authors" array, and any contributor GitHub usernames to the "contributors" array.

🎶 Implementation Notes

• Example code should only use syntax & concepts introduced within these docs or one of the prerequisite concept exercises or documents. Where possible, please use REPL formatting, unless you are demonstrating pseudo code or a long code block. Please do not use syntax not previously covered in prerequisite topics or exercises. Please also follow PEP8 guidelines.
• Our markdown and JSON files are checked against prettier . We recommend setting prettier up locally and running it prior to submitting your PR to avoid any CI errors.

🆘 Next Steps & Getting Help

1. If you'd like to work on this issue, comment saying "I'd like to work on this" (there is no real need to wait for a response, just go ahead, we'll assign you and put a [claimed] label on the issue).
2. If you have any questions while implementing, please post the questions as comments in here, or contact one of the maintainers on our Slack channel.