[Python] Implement new Concept Exercise: in

[DavidGerva]

This issue describes how to implement the membership testing 'in' operator 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:

• The features of v3.
• Rationale for v3.
• What are concept exercise and how they are structured?

Please also watch the following video:

• The Anatomy of a Concept Exercise.

Goal

This concept exercise should convey a basic understanding of the in operator in Python to perform a membership testing.

Learning objectives

• use the in operator to tests if an object is (not) a member of a collection

Out of scope

• identity testing via is and is not
• comparisons

Concepts

• in operator
• membership

Prerequisites

• basics
• booleans, True, False
• dicts
• lists
• sets
• tuples

Resources to refer to

• The in operator
• Membership testing (Python docs)

Hints

• One or more of the links above or analogous links from a trusted source.

After

Nothing

Representer

No changes required.

Analyzer

No changes required.

Implementing

Tests should be written using unittest.TestCase and the test file named in_test.py.

Help

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

Edits

[aimorris]

This should be in the collections concept exercise where you can explain everything about collections, including the in keyword.

[BethanyG]

Ooof. @DavidGerva -- After going back over this twice, I have to agree with @aimorris - we should do membership checking alongside each data structure, and not try to making it it's own exercise. Having checked tuples and lists -- we're already doing that, so I am going to close this as no longer relevant. Apologies for having you do extra work. 😦 .

[BethanyG]

If there is a strong disagreement, please re-open.

[SleeplessByte]

(I agree with the decision of adding in to each data structure's exercise.)