OLD iterators Concept Exercise

[BethanyG]

This issue describes how to implement the iterators concept exercise for the python track.

Getting started

Please 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. So, before diving into the implementation, please read up on the following documents:

• Contributing to Exercism | Exercism and GitHub | Contributor Pull Request Guide
• What are those Weird Task Tags about?
• Building Language Tracks: An Overview
• What are Concepts?
• Concept Exercise Specifications
• Concept Specifications
• Exercism Formatting and Style Guide
• Exercism Markdown Specification
• Reputation

Goal

This concept exercise is meant to teach an understanding/creation/use of iterators 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

• 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

• loops
• iteration
• iterators & iterator types
• iterator protocol
• iterables
• enumeration

Prerequisites

These are the concepts/concept exercises the student needs to complete/understand before solving this concept exercise.

• 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

• 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: eumulating 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

• Hints

  For more information on writing hints see hints

  • You can refer to one or more of the resources linked above, or analogous resources from a trusted source. We prefer using links within the Python Docs as the primary go-to, but other resources listed above are also good. Please try to avoid paid or subscription-based links if possible.

• 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 Description

Please see the following for more details on these files: concepts & concept exercises

• Concept about.md

  Concept file/issue: There is currently no issue or files for the concept. They are TBD.

  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 document listed above, and will provide a brief introduction of the concept for a student who has not yet completed the concept exercise. It should contain a good summation of the concept, but not go into lots of detail.

• Exercise introduction.md

  For more information, see Exercise introduction.md

  • This should also summarize/paraphrase the above document, but with enough information and examples for the student to complete the tasks outlined in this concept exercise.

Test-runner

No changes required to the Python Test Runner at this time.

Representer

No changes required to the Python Representer at this time.

Analyzer

No changes required to the Python Analyzer at this time.

Exercise Metadata - Track

For more information on concept exercises and formatting for the Python track config.json , please see concept exercise metadata. The track config.json file can be found in the root of the Python repo.

You can use the below for the exercise UUID. You can also generate a new one via exercism configlet, uuidgenerator.net, or any other favorite method. The UUID must be a valid V4 UUID.

• Exercise UUID : 087e3eec-33f4-4b7e-8335-a5ee9ddda9f3
• concepts should be filled in from the Concepts section in this issue
• prerequisites should be filled in from the Prerequisites section in this issue

Exercise Metadata Files Under .meta/config.json

For more information on exercise .meta/ files and formatting, see concept exercise metadata files

• .meta/config.json - see this link for the fields and formatting of this file.
• .meta/design.md - see this link for the formatting of this file. Please use the Goal, Learning Objectives,Concepts, Prerequisites and , Out of Scope sections from this issue.

Implementation Notes

• Code in the .meta/examplar.py file should only use syntax & concepts introduced in this exercise or one of its prerequisite exercises.
• Please do not use comprehensions, generator expressions, or other syntax not previously covered. Please also follow PEP8 guidelines.
• In General, tests should be written using unittest.TestCase and the test file should be named <EXERCISE-NAME>_test.py.
• While we do use PyTest as our test runner and for some implementation tests, please check with a maintainer before using a PyTest test method, fixture, or feature.
• 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.

Help

If you have any questions while implementing the exercise, please post the questions as comments in this issue, or contact one of the maintainers on our Slack channel.