psf--black/docs/integrations/doctest_formatting.md

# Doctest Formatting

While _Black_ makes some decisions about styling for docstrings, it does not make any
assumptions about the contents of documentation. Thus, executable Python code inside
docstrings or documentation files (e.g. doctests), will not be formatted by _Black_.

Listed below are tools that apply _Black_ formatting to code inside docstrings and
documentation files.

> Note: There are some observed inconsistencies between the below packages. Because of
> this, we hesitate to make any recommendations. Any installed packages are installed at
> your own risk. We also encourage anyone to contribute documentation for additional
> packages that apply _Black_ formatting to doctests.

## blacken-docs

[`blacken-docs`](https://github.com/adamchainz/blacken-docs) is primarily used to apply
_Black_ formatting to code in documentation files (e.g. `.rst`, `.md`, `.tex`).

`blacken-docs` supports the following:

- Python code blocks in Markdown, reStructuredText, and LaTeX files. Similar to
  `blackdoc`, normal _Black_ formatting is applied, so doctests inside Python code
  blocks will not be formatted.

  ````md
  ```python
  print("Hello world!")
  ```
  ````

  ```rst
  .. code-block:: python
      print("Hello world!")
  ```

  ```latex
  \begin{minted}{python}
  print("Hello world!")
  \end{minted}
  ```

- Doctests inside Pycon code blocks in Markdown and reStructuredText. The code blocks
  may be included in a `.md` or `.rst` file, or inside a docstring in a Python file.

  ````md
  ```python
  >>> print("Hello world!")
  ```
  ````

  ```rst
  .. code-block:: pycon
      >>> print("Hello world!")
  ```

  ````python
  def add_one(n: int) -> int:
      """
      Examples
      --------
      ```pycon
      >>> add_one(1) == 2
      ```
      """
      return n + 1
  ````

## blackdoc

[`blackdoc`](https://blackdoc.readthedocs.io/en/stable) is primarily used to apply
_Black_ formatting to doctests in Python files. It will not format any file contents
that are otherwise covered by _Black_.

`blackdoc` supports the following:

- Doctests in Python files.

  ```python
  def add_one(n: int) -> int:
      """
      Examples
      --------
      >>> add_one(1) == 2
      """
      return n + 1
  ```

- Python code blocks in Markdown or reStructuredText files. In these cases, normal
  _Black_ formatting is applied, i.e., doctests inside Python code blocks will not be
  formatted.

  ````md
  ```python
  print("Hello world!")
  ```
  ````

  ```rst
  .. code-block:: python
      print("Hello world!")
  ```