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# `sphinx.ext.napoleon` – Support for NumPy and Google style docstrings

Module author: Rob Ruana

New in version 1.3.

## Napoleon - Marching toward legible docstrings

Are you tired of writing docstrings that look like this:

    :param path: The path of the file to wrap
    :type path: str
    :param field_storage: The :class:`FileStorage` instance to wrap
    :type field_storage: FileStorage
    :param temporary: Whether or not to delete the file when the File
       instance is destructed
    :type temporary: bool
    :returns: A buffered writable file descriptor
    :rtype: BufferedFileStorage

ReStructuredText is great, but it creates visually dense, hard to read docstrings. Compare the jumble above to the same thing rewritten according to the Google Python Style Guide:

    Args:
        path (str): The path of the file to wrap
        field_storage (FileStorage): The :class:`FileStorage` instance to wrap
        temporary (bool): Whether or not to delete the file when the File
           instance is destructed

    Returns:
        BufferedFileStorage: A buffered writable file descriptor

Much more legible, no?

Napoleon is a Sphinx Extensions that enables Sphinx to parse both NumPy and Google style docstrings - the style recommended by Khan Academy.

Napoleon is a pre-processor that parses NumPy and Google style docstrings and converts them to reStructuredText before Sphinx attempts to parse them. This happens in an intermediate step while Sphinx is processing the documentation, so it doesn’t modify any of the docstrings in your actual source code files.

### Getting Started

1. After setting up Sphinx to build your docs, enable napoleon in the Sphinx conf.py file:

       # conf.py

       # Add autodoc and napoleon to the extensions list
       extensions = ['sphinx.ext.autodoc', 'sphinx.ext.napoleon']

2. Use sphinx-apidoc to build your API documentation:

       $ sphinx-apidoc -f -o docs/source projectdir

### Docstrings

Napoleon interprets every docstring that `autodoc` can find, including docstrings on: `modules`, `classes`, `attributes`, `methods`, `functions`, and `variables`. Inside each docstring, specially formatted Sections are parsed and converted to reStructuredText.

All standard reStructuredText formatting still works as expected.

### Docstring Sections

All of the following section headers are supported:

> - `Args` (alias of Parameters)
> - `Arguments` (alias of Parameters)
> - `Attributes`
> - `Example`
> - `Examples`
> - `Keyword Args` (alias of Keyword Arguments)
> - `Keyword Arguments`
> - `Methods`
> - `Note`
> - `Notes`
> - `Other Parameters`
> - `Parameters`
> - `Return` (alias of Returns)
> - `Returns`
> - `Raises`
> - `References`
> - `See Also`
> - `Todo`
> - `Warning`
> - `Warnings` (alias of Warning)
> - `Warns`
> - `Yield` (alias of Yields)
> - `Yields`

### Google vs NumPy

Napoleon supports two styles of docstrings: Google and NumPy. The main difference between the two styles is that Google uses indention to separate sections, whereas NumPy uses underlines.

Google style:

    def func(arg1, arg2):
        """Summary line.

        Extended description of function.

        Args:
            arg1 (int): Description of arg1
            arg2 (str): Description of arg2

        Returns:
            bool: Description of return value

        """
        return True

NumPy style:

    def func(arg1, arg2):
        """Summary line.

        Extended description of function.

        Parameters
        ----------
        arg1 : int
            Description of arg1
        arg2 : str
            Description of arg2

        Returns
        -------
        bool
            Description of return value

        """
        return True

NumPy style tends to require more vertical space, whereas Google style tends to use more horizontal space. Google style tends to be easier to read for short and simple docstrings, whereas NumPy style tends be easier to read for long and in-depth docstrings.

The Khan Academy recommends using Google style.

The choice between styles is largely aesthetic, but the two styles should not be mixed. Choose one style for your project and be consistent with it.

See also

For complete examples:

- Example Google Style Python Docstrings
- Example NumPy Style Python Docstrings

### Type Annotations

PEP 484 introduced a standard way to express types in Python code. This is an alternative to expressing types directly in docstrings. One benefit of expressing types according to PEP 484 is that type checkers and IDEs can take advantage of them for static code analysis.

Google style with Python 3 type annotations:

    def func(arg1: int, arg2: str) -> bool:
        """Summary line.

        Extended description of function.

        Args:
            arg1: Description of arg1
            arg2: Description of arg2

        Returns:
            Description of return value

        """
        return True

Google style with types in docstrings:

    def func(arg1, arg2):
        """Summary line.

        Extended description of function.

        Args:
            arg1 (int): Description of arg1
            arg2 (str): Description of arg2

        Returns:
            bool: Description of return value

        """
        return True

Note

Python 2/3 compatible annotations aren’t currently supported by Sphinx and won’t show up in the docs.

## Configuration

Listed below are all the settings used by napoleon and their default values. These settings can be changed in the Sphinx conf.py file. Make sure that both “sphinx.ext.autodoc” and “sphinx.ext.napoleon” are enabled in conf.py:

    # conf.py

    # Add any Sphinx extension module names here, as strings
    extensions = ['sphinx.ext.autodoc', 'sphinx.ext.napoleon']

    # Napoleon settings
    napoleon_google_docstring = True
    napoleon_numpy_docstring = True
    napoleon_include_init_with_doc = False
    napoleon_include_private_with_doc = False
    napoleon_include_special_with_doc = True
    napoleon_use_admonition_for_examples = False
    napoleon_use_admonition_for_notes = False
    napoleon_use_admonition_for_references = False
    napoleon_use_ivar = False
    napoleon_use_param = True
    napoleon_use_rtype = True

`napoleon_google_docstring`

  True to parse Google style docstrings. False to disable support for Google style docstrings. Defaults to True.

`napoleon_numpy_docstring`

  True to parse NumPy style docstrings. False to disable support for NumPy style docstrings. Defaults to True.

`napoleon_include_init_with_doc`

  True to list `__init___` docstrings separately from the class docstring. False to fall back to Sphinx’s default behavior, which considers the `__init___` docstring as part of the class documentation. Defaults to False.

  If True:

      def __init__(self):
          \"\"\"
          This will be included in the docs because it has a docstring
          \"\"\"

      def __init__(self):
          # This will NOT be included in the docs

`napoleon_include_private_with_doc`

  True to include private members (like `_membername`) with docstrings in the documentation. False to fall back to Sphinx’s default behavior. Defaults to False.

  If True:

      def _included(self):
          """
          This will be included in the docs because it has a docstring
          """
          pass

      def _skipped(self):
          # This will NOT be included in the docs
          pass

`napoleon_include_special_with_doc`

  True to include special members (like `__membername__`) with docstrings in the documentation. False to fall back to Sphinx’s default behavior. Defaults to True.

  If True:

      def __str__(self):
          """
          This will be included in the docs because it has a docstring
          """
          return unicode(self).encode('utf-8')

      def __unicode__(self):
          # This will NOT be included in the docs
          return unicode(self.__class__.__name__)

`napoleon_use_admonition_for_examples`

  True to use the `.. admonition::` directive for the Example and Examples sections. False to use the `.. rubric::` directive instead. One may look better than the other depending on what HTML theme is used. Defaults to False.

  This NumPy style snippet will be converted as follows:

      Example
      -------
      This is just a quick example

  If True:

      .. admonition:: Example

         This is just a quick example

  If False:

      .. rubric:: Example

      This is just a quick example

`napoleon_use_admonition_for_notes`

  True to use the `.. admonition::` directive for Notes sections. False to use the `.. rubric::` directive instead. Defaults to False.

  Note

  The singular Note section will always be converted to a `.. note::` directive.

  See also

  `napoleon_use_admonition_for_examples`

`napoleon_use_admonition_for_references`

  True to use the `.. admonition::` directive for References sections. False to use the `.. rubric::` directive instead. Defaults to False.

  See also

  `napoleon_use_admonition_for_examples`

`napoleon_use_ivar`

  True to use the `:ivar:` role for instance variables. False to use the `.. attribute::` directive instead. Defaults to False.

  This NumPy style snippet will be converted as follows:

      Attributes
      ----------
      attr1 : int
          Description of `attr1`

  If True:

      :ivar attr1: Description of `attr1`
      :vartype attr1: int

  If False:

      .. attribute:: attr1

         *int*

         Description of `attr1`

`napoleon_use_param`

  True to use a `:param:` role for each function parameter. False to use a single `:parameters:` role for all the parameters. Defaults to True.

  This NumPy style snippet will be converted as follows:

      Parameters
      ----------
      arg1 : str
          Description of `arg1`
      arg2 : int, optional
          Description of `arg2`, defaults to 0

  If True:

      :param arg1: Description of `arg1`
      :type arg1: str
      :param arg2: Description of `arg2`, defaults to 0
      :type arg2: int, optional

  If False:

      :parameters: * **arg1** (*str*) --
                     Description of `arg1`
                   * **arg2** (*int, optional*) --
                     Description of `arg2`, defaults to 0

`napoleon_use_keyword`

  True to use a `:keyword:` role for each function keyword argument. False to use a single `:keyword arguments:` role for all the keywords. Defaults to True.

  This behaves similarly to `napoleon_use_param`. Note unlike docutils, `:keyword:` and `:param:` will not be treated the same way - there will be a separate “Keyword Arguments” section, rendered in the same fashion as “Parameters” section (type links created if possible)

  See also

  `napoleon_use_param`

`napoleon_use_rtype`

  True to use the `:rtype:` role for the return type. False to output the return type inline with the description. Defaults to True.

  This NumPy style snippet will be converted as follows:

      Returns
      -------
      bool
          True if successful, False otherwise

  If True:

      :returns: True if successful, False otherwise
      :rtype: bool

  If False:

      :returns: *bool* -- True if successful, False otherwise