#  Contributing

👋🏽 👋  Hi.  Thank you so much for your interest in contributing to the Python track!  **We are happy you are here.**🌟 :tada:


`exercsim/Python` is  one of the many tracks on [exercism](https://exercism.org/).   This repo holds all the instructions, tests, code, & support files for Python *exercises* currently under development or implemented & available for students.

Exercises are grouped into  **concept** exercises which teach the [Python syllabus](https://exercism.org/tracks/python/concepts), and  **practice** exercises, which are unlocked by progressing in the syllabus tree.  Practice exercises are open-ended, and can be used to practice  concepts learned, try out new techniques, and _play_.  These two exercise groupings can be found in the track [`config.json`](https://github.com/exercism/javascript/blob/main/config.json), and under the `python/exercises` directory.



#### 🐛 **Did you find a bug?**

It's not uncommon that people discover typos, confusing directions, or incorrect implementations of  certain tests or code examples.  Or you might have a great suggestion for a hint to aid students (💙) ,  see optimizations for exemplar or test code, find some missing test cases to add, or want to correct factual and/or logical errors.  Or maybe you have a great idea for an exercise or feature.

_Our track is always a work in progress!_ 🌟🌟   Please  📛  [Open an issue](https://github.com/exercism/python/issues/new/choose)  📛 , and let us know what you've found.



#### 🚧  **Did you write a patch that fixes a bug? **

 💛 💙 **We Warmly Welcome Pull Requests that are:**

             1️⃣     Small, contained fixes for typos/grammar/punctuation/code syntax on [one] exercise,
             2️⃣     Medium changes that have been agreed/discussed via a filed issue,  
             3️⃣     Contributions from our [help wanted](https://github.com/exercism/python/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22) issue list,
             4️⃣     Larger (_and previously agreed-upon_) contributions from recent & regular (_within the last 6 months_) contributors.

When in doubt,   📛  [Open an issue](https://github.com/exercism/python/issues/new/choose)  📛.  We'll happily discuss your proposed change. 🐍

But let's talk before you take a whole lot of  time implementing anything.



####  :books:  **Want to jump directly into Exercism specifications & detail? **

[Track Structure](https://github.com/exercism/docs/tree/main/building/tracks) **|** [Tasks](https://exercism.org/docs/building/product/tasks) **|** [Concepts](https://github.com/exercism/docs/blob/main/building/tracks/concepts.md) **|** [Concept Exercises](https://github.com/exercism/docs/blob/main/building/tracks/concept-exercises.md) **|** [Practice Exercises](https://github.com/exercism/docs/blob/main/building/tracks/practice-exercises.md) **|** [Presentation](https://github.com/exercism/docs/blob/main/building/tracks/presentation.md) **|** [ Style Guide for Writing](https://github.com/exercism/docs/blob/main/building/markdown/style-guide.md) **|** [Markdown Specification](https://github.com/exercism/docs/blob/main/building/markdown/markdown.md)



## The Exercism Community



🌟🌟 If you have not already done so, please take a moment to read our  [Code of Conduct](https://exercism.org/docs/using/legal/code-of-conduct) & [Being a Good Community Member](https://github.com/exercism/docs/tree/main/community/good-member) .  It might also be helpful to take a look at [The words that we use](https://github.com/exercism/docs/blob/main/community/good-member/words.md).



Some defined roles in our community:  [Community Member](https://github.com/exercism/docs/tree/main/community/good-member) |  [Contributors](https://github.com/exercism/docs/blob/main/community/contributors.md) |[Mentors](https://github.com/exercism/docs/tree/main/mentoring) |  [Maintainers](https://github.com/exercism/docs/blob/main/community/maintainers.md) | [Admins](https://github.com/exercism/docs/blob/main/community/administrators.md)



## In General



- Pull requests should be focused on a single exercise, issue, or change.
- PR titles and descriptions should make clear **what** has changed and **why**. Please link 🔗  to any related issues the PR addresses.
- 📛  [An issue should be opened](https://github.com/exercism/python/issues/new/choose)  📛 _**before**_ creating a PR that makes significant or breaking change to an existing exercise.  The same holds true for  changes across multiple exercises. It is best to discuss these changes with 🧰  maintainers before doing the work.
- Follow coding standards found in [PEP8](https://www.python.org/dev/peps/pep-0008/) ( ["For Humans" version here](https://pep8.org/).)  We do have some more specific requirements.  More on that later.
- All files should have a proper [EOL](https://en.wikipedia.org/wiki/Newline) at the end. This means one carriage return at the end of the final line of text in files.
- Watch out otherwise for trailing spaces, extra blank lines, and spaces in blank lines. ⚠️
- The CI is going to run **a lot** of check on your PR. Pay attention to the failures, try to understand and fix them.  If you need help, comment in the PR or issue. 🙋🏽‍♀️



## A Little More on Writing Style and Standards



Non-code content (_exercise introductions & instructions, hints, concept write-ups, documentation etc._) should be written in [American English](https://github.com/exercism/docs/blob/main/building/markdown/style-guide.md) .  We strive to watch [the words we use](https://github.com/exercism/docs/blob/main/community/good-member/words.md).

When a usage is contested or ambiguous, we default to what is best understood by our international community of learners, even if it "sounds a little weird"  to a "native" American English speaker.

Our documents use [Markdown](https://guides.github.com/pdfs/markdown-cheatsheet-online.pdf) , with certain [alterations](https://github.com/exercism/docs/blob/main/building/markdown/widgets.md) & [additions](https://github.com/exercism/docs/blob/main/building/markdown/internal-linking.md).  Here is our full [Markdown Specification](https://github.com/exercism/docs/blob/main/building/markdown/markdown.md).  We format/lint our Markdown with [Prettier](https://prettier.io/).



##  A Little More on Exercises

- Each exercise must stand on its own. Please do not use or reference files outside the exercise directory. "Outside" files will not be included if a  student fetches the exercise via the CLI.

- Each exercise/problem should have a complete  test suite, an example/exemplar solution, and a stub file ready for student implementation.

  - See  [Concept Exercise Anatomy](https://github.com/exercism/docs/blob/main/building/tracks/concept-exercises.md),  or  [Practice Exercise Anatomy](https://github.com/exercism/docs/blob/main/building/tracks/practice-exercises.md) depending on to which type of exercise you are contributing.

- For **practice exercises**, descriptions and instructions come from a centralized cross-track  [problem specifications](https://github.com/exercism/problem-specifications) repository. Any updates or changes need to be proposed/approved in that repository first. If Python-specific changes become necessary, they  need to be appended to the canonical instructions by creating a `instructions.append.md` file in this repository.

- **Practice Exericse Test Suits** for many exercises are similarly [auto-generated]() from data in  [problem specifications](https://github.com/exercism/problem-specifications).  **Any changes to them need to be proposed/discussed in that repository, and approved by 3 track maintainers.** If Python-specific changes become necessary, they can be appended to this tracks `tests.toml` file.   📛  [**Please file an issue**](https://github.com/exercism/python/issues/new/choose)  📛  and check with maintainers before adding  any Python-specific tests.



## Python Coding Standards





## Python Versions

Exercises on this track officially support Python >= `3.8`  Track tooling (`test runners`, `analyzers`, and r`epresenters`)  all run on Python `3.9`.

*  All exercises going forward should be written for compatibility with Python >= `3.8`,.
* Version backward _incompatibility_ (*e.g* an exercise using a `3.8` or `3.9` only feature)  should be clearly notied in any exercise introduction or notes.

* _Most_ exercises will work with Python 3.6+, and _many_ are compatible with Python 2.7+.   Please do not change existing exercises to add new `3.6`+ features without consulting with a maintainer first.

- All test suites and example solutions must work in all Python versions that we currently support. When in doubt about a feature, please check with maintainers.



## External Libraries and Dependencies





## Auto-Generated Test Files and Test Templates



Practice exericses  inherit their definitions from the [problem-specifications](https://github.com/exercism/problem-specifications) repository in the form of _description files_.  Exercise introductions, instructions and (_in the case of **many**, but not **all**_) test files are machine-generated .

Changes to practice exercise _specifications_ should be raised/PR'd in  [problem-specifications](https://github.com/exercism/problem-specifications)  and approved by **3 track maintainers**.  After an exercise change has gone through that process , related documents and tests for the Python track will need to be re-generated  via  [configlet](https://github.com/exercism/docs/blob/main/building/configlet/generating-documents.md).  Configlet is also used as part of the track CI, essential track and exercise linting,  and other verification tasks.

If a practice exercise has an auto-generated `<exercise>_test.py` file, there will be a  `.meta/template.j2` and a `.meta/tests.toml` file  in the exercise directory.   If an exercise implements  Python track-specific tests, there may be a `.meta/additional_tests.json` to define them.  These `additional_tests.json` files will automatically be included in test generation.

Practice exercise  `<exercise>_test.py`  files are  generated/regenerated via the [Python Track Test Generator](https://github.com/exercism/python/blob/main/docs/GENERATOR.md).   Please reach out to a maintainer if you need any help with the process.



## Tools and Tooling


##################################


## Architecture

Exercism tracks inherit exercise definitions from the [problem-specifications] repository in the form of description files
(from which exercise READMEs are [generated](#generating-exercise-readmes))


## Implementing an exercise

### Exercise structure

```Bash
exercises/[EXERCISE]/
├── [EXERCISE].py
├── [EXERCISE]_test.py
├── example.py
├── .meta
│   ├── template.j2
│   ├── additional_tests.json
│   └── hints.md
└── README.md
```

Files:

| File | Description | Source |
|:--- |:--- |:--- |
| [[EXERCISE].py](exercises/two-fer/two_fer.py) | Solution stub  | Manually created by the implementer |
| [[EXERCISE]_test.py](exercises/two-fer/two_fer_test.py) | Exercise test suite | Automatically generated if `.meta/template.j2` is present, otherwise manually created by the implementer |
| [example.py](exercises/two-fer/example.py) | Example solution used to automatically verify the `[EXERCISE]_test.py` suite | Manually created by the implementer |
| [.meta/template.j2](exercises/two-fer/.meta/template.j2) | Test generation template; if present used to automatically generate `[EXERCISE]_test.py` (See [generator documentation](docs/GENERATOR.md)) | Manually created by implementer |
| [.meta/additional_tests.json](exercises/word-count/.meta/additional_tests.json) | Defines additional track-specific test cases; if `.meta/template.j2` is also present these test will be incorporated into the automatically generated `[EXERCISE]_test.py` | Manually created by the implementer |
| [.meta/hints.md](exercises/high-scores/.meta/hints.md) | Contains track-specific hints that are automatically included in the generated `README.md` file | Manually created by the implementer |
| [README.md](exercises/two-fer/README.md) | Exercise README | [Generated by `configlet` tool](#generating-exercise-readmes) |

### Generating Exercise READMEs

#### Requirements
- A local clone of the [problem-specifications] repository.
- [configlet]: may be obtained either by
  - (**Recommended**) Following installation instructions at the above link
  - Running `bin/fetch-configlet` (`configlet` binary will be downloaded to the repository `bin/`)

#### Generating all READMEs

```
configlet generate <path/to/track> --spec-path path/to/problem/specifications
```

#### Generating a single README

```
configlet generate <path/to/track> --spec-path path/to/problem/specifications --only example-exercise
```

### Implementing tests

If an unimplemented exercise has a `canonical-data.json` file in the [problem-specifications] repository, a generation template must be created. See the [test generator documentation](docs/GENERATOR.md) for more information.

If an unimplemented exercise does not have a `canonical-data.json` file, the test file must be written manually (use existing test files for examples).

### Example solutions

Example solution files serve two purposes:

1. Verification of the tests
2. Example implementation for mentor/student reference

### config.json

[`config.json`](config.json) is used by the website to determine which exercises to load an in what order. It also contains some exercise metadata, such as difficulty, labels, and if the exercise is a core exercise. New entries should be places just before the first exercise that is marked `"deprecated": true`:

```JSON
    {
      "slug": "current-exercise",
      "uuid": "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa",
      "core": false,
      "unlocked_by": null,
      "difficulty": 1,
      "topics": [
          "strings"
      ]
    },
    <<< HERE
    {
      "slug": "old-exercise",
      "uuid": "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa",
      "core": false,
      "unlocked_by": null,
      "difficulty": 2,
      "topics": null,
      "status": "deprecated"
    },
```

Fields
<table>
<tr>
    <td>slug</td>
    <td>Hyphenated lowercase exercise name</td>
</tr>
<tr>
    <td>uuid</td>
    <td>Generate using <code>configlet uuid</code></td>
</tr>
<tr>
    <td>core</td>
    <td>Set to <code>false</code>; core exercises are decided by track maintainers</td>
</tr>
<tr>
    <td>unlocked_by</td>
    <td>Slug for the core exercise that unlocks the new one</td>
</tr>
<tr>
    <td>difficulty</td>
    <td><code>1</code> through <code>10</code>. Discuss with reviewer if uncertain.</td>
</tr>
<tr>
    <td>topics</td>
    <td>Array of relevant topics from the <a href="https://github.com/exercism/problem-specifications/blob/master/TOPICS.txt">topics list</a> </td>
</tr>
</table>


## Implementing Track-specific Exercises

Similar to implementing a canonical exercise that has no `canonical-data.json`, but the exercise README will also need to be written manually. Carefully follow the structure of generated exercise READMEs.


## Pull Request Tips

Before committing:
- Run `configlet fmt` and `configlet lint` before committing if [`config.json`](config.json) has been modified
- Run [flake8] to ensure all Python code conforms to style standards
- Run `test/check-exercises.py [EXERCISE]` to check if your test changes function correctly
- If you modified or created a `hints.md` file, [regenerate the README](#generating-exercise-readmes)
- If your changes affect multiple exercises, try to break them up into a separate PR for each exercise.


[configlet]: https://github.com/exercism/configlet
[Exercism contributing guide]: https://github.com/exercism/docs/blob/master/contributing-to-language-tracks/README.md
[problem-specifications]: https://github.com/exercism/problem-specifications
[topics list]: https://github.com/exercism/problem-specifications/blob/master/TOPICS.txt
[flake8]: http://flake8.pycqa.org/