[New Concept Exercise] : list-comprehensions

[BethanyG]

This issue describes how to implement the list-comprehensions 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

The goal of this exercise is to teach the syntax and variants of list comprehensions in Python.

Learning objectives

• Understand how a list comprehension relates to the loop + append method of creating/computing a List.
• Create a list comprehension from a loop + append
• Create a list comprehension from a string, List, or other iterable (such as zip() or dict.items())
• Use one or more conditions/operators/methods to filter comprehension inputs
• Use methods or logic to format the elements (output members) of the comprehension
• Create a nested comprehension
• Create a nested comprehension with one or more formatting or filtering conditions

Out of scope

• Memory and performance characteristics and optimizations
• generators and generator expressions in list comprehensions
• How map() and filter() relate to or differ from list comprehensions
• Using the assignment expression (walrus operator) with a list comprehension

Concepts

• list-comprehensions

Prerequisites

• basics
• bools
• comparisons
• conditionals
• lists
• list-methods
• loops
• iteration
• sequences

Resources to refer to

• List Comprehensions (Python official docs)
• Nested List Comprehensions (Python official docs)
• When to Use a List Comprehension in Python (Real Python)
• Python List Comprehensions: Explained Visually (Trey Hunner)

Hints

• List Comprehensions section of the Python docs tutorial: List Comprehensions
• This animated GIF from Trey Hunner: List Comprehensions: The Movie

After

• comprehension syntax for other data structures such as sets and dictionaries
• generators and generator expressions
• generators and generator expressions in list comprehensions

Representer

No changes required.

Analyzer

No changes rquired.

Implementing

• Tests should be written using unittest.TestCase, and the test file named list_comprehensions_test.py.
• How to Implement a Concept Exercise in Python
• make-concept-exercise Utility

Help

If you have any questions while implementing the exercise, please post the questions as comments in this issue.

[github-actions]

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