[New Concept Docs]: Class Customization

[BethanyG]

This issue describes how to implement the class-customization 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 documents are meant to teach an understanding/use of class-customization in Python.

💡 Learning objectives

• more fully understand the uses (and possible abuses) of classes in Python

• understanding of class members

• understand some of the options that can be used to adapt a class for purposes beyond simple object creation, including:

  • using @staticmethod to provide namespaced functionality without object instantiation.
  • using @classmethod to provide functionality that modifies class attributes shared across class instances
  • using __repr__() and __str__() to provide human-readable and understandable class descriptions.

• using property() and @property to make getters and setters for the methods of a class

  • using property() and @property to "compose" or "calculate" and return instance attributes.
  • using property() and @property to "protect" an attribute from mutation.

• using functools.cached_property() to calculate a property via a method, and the cache it for future calls to the property.

• Pythons version of "non-public" methods and "private variables" (AKA Name mangling)

🚫 Out of scope

Concepts and Subjects that are Out of Scope

• class-inheritance, multiple-inheritance, __super()__, class mixins
• class-composition -- (beyond the composition needed for the decorators in this exercise)
• dataclasses
• decorators outside of @property, @staticmethod, and @classmethod (the student should already be exposed to the function version of these in a prerequisite)
• generators
• coroutines
• descriptors (these will get their own exercise)
• using a class as a decorator
• performance considerations

🤔 Concepts

Concepts and Related Concepts this Concept Covers

• classes
• class attributes
• class members
• class methods, @classmethod
• static methods, @staticmethod
• decorators
• getters & setters (through the use of property() and @property)
• instance attributes
• instance methods
• non-public methods, private variables, and name-mangling

↩️ Prerequisites

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

Prereqs

• basics
• booleans
• classes
• comparisons
• decorators
• dicts
• functions
• higher-order-functions
• iteration
• lists
• numbers
• sequences
• sets
• strings
• tuples

📚 Resources to refer to

Resources

• classes (Python tutorial)
• private variables (Python tutorial)
• Python Data Model - Python Docs
• class property() - (Python Docs)
• Real Python: Python's Instance, Class, and Static Methods Demystified
• Real Python: Object-Oriented Programming in Python 3

📁 Files to Be Created

File Detail for this Exercise

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.