[New Concept Docs]: Unpacking & Multiple Assignment in Python

[BethanyG]

This issue describes how to implement the unpacking and multiple assignment 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/use of unpacking and the * (splat) and ** (double splat) operators in Python.

💡 Learning objectives

• Understand/use unpacking through the use of * and ** prefix operators in various scenarios
  • * and ** as prefixes ..... not to be confused with * (multiply) and ** (exponentiation) as infix, or mathematical operators
  • what happens in the process of "unpacking" - form, ordering, & iteration
  • use in arguments to functions
  • use in argument capture for functions (aka passing an arbitrary number of arguments -- *args * & **kwargs)
  • use in defining keyword only arguments
  • use in iterable (mainly tuple and list) unpacking & packing
  • use in dict unpacking & packing
• Understand/use unpacking via multiple assignment
  • using multiple assignment in place of indexing
  • using multiple assigment + * in place of slicing
  • using "list-like" syntax & "tuple-like" syntax
  • unpacking plus "leftovers" via *
• Differences between straight multiple assignment and * & **
• Deep unpacking

🚫 Out of scope

Concepts & Subjects that are Out of Scope (click to open)

• classes
• comprehensions
• comprehensions in lambdas
• map(), filter() or functools.reduce() in a comprehension
• function-arguments beyond explaining briefly how *, ** work in function arguments, and how * works in requiring arguments.
• functools beyond functools.reduce()(this will get its own exercise)
• generators
• using an assignment expression or "walrus" operator (:=) alone or in a lambda

🤔 Concepts

Concepts & Related Concepts Covered (click to open)

• unpacking
• unpacking generalizations
• multiple assignment

↩️ Prerequisites

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

Prereqs (click to open)

• basics
• bools
• comparisons
• dicts
• dict-methods
• functions
• function-arguments
• higher-order-functions
• functional tools
• Identity methods is and is not
• iteration
• lists
• list-methods
• numbers
• sequences
• sets
• strings
• string-methods
• tuples

📚 Resources to refer to

Resources (click to open)

• Trey Hunner: Asterisks in Python - what they are and how to use them
• Trey Hunner: Multiple assignment and tuple unpacking improve Python code readability
• Dan Bader: Python Nested Unpacking
• PEP 3132: Extended Iterable Unpacking
• PEP 0448: Additional Unpacking Generalizations
• Python Tutorial: Arbitrary Argument Lists & Python Tutorial: Unpacking Argument Lists
• Python Docs: Expression Lists
• Python Docs: Defining Functions
• built-ins: Python Docs

📁 Files to Be Created

File Detail for this Exercise (click to collapse)

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.