sphinx-autodoc-typehints

This extension allows you to use Python 3 annotations for documenting acceptable argument types and return value types of functions. See an example of the Sphinx render at the pyproject-api docs.

This allows you to use type hints in a very natural fashion, allowing you to migrate from this:

def format_unit(value, unit):
    """
    Formats the given value as a human readable string using the given units.

    :param float|int value: a numeric value
    :param str unit: the unit for the value (kg, m, etc.)
    :rtype: str
    """
    return f"{value} {unit}"

to this:

from typing import Union


def format_unit(value: Union[float, int], unit: str) -> str:
    """
    Formats the given value as a human readable string using the given units.

    :param value: a numeric value
    :param unit: the unit for the value (kg, m, etc.)
    """
    return f"{value} {unit}"

Installation and setup

First, use pip to download and install the extension:

pip install sphinx-autodoc-typehints

Then, add the extension to your conf.py:

extensions = ["sphinx.ext.autodoc", "sphinx_autodoc_typehints"]

Options

The following configuration options are accepted:

typehints_fully_qualified (default: False): if True, class names are always fully qualified (e.g. module.for.Class). If False, just the class name displays (e.g. Class)
always_document_param_types (default: False): If False, do not add type info for undocumented parameters. If True, add stub documentation for undocumented parameters to be able to add type info.
always_use_bars_union (default: False): If True, display Union's using the | operator described in PEP 604. (e.g X | Y or int | None). If False, Unions will display with the typing in brackets. (e.g. Union[X, Y] or Optional[int])
typehints_document_rtype (default: True): If False, never add an :rtype: directive. If True, add the :rtype: directive if no existing :rtype: is found.
typehints_use_rtype (default: True): Controls behavior when typehints_document_rtype is set to True. If True, document return type in the :rtype: directive. If False, document return type as part of the :return: directive, if present, otherwise fall back to using :rtype:. Use in conjunction with napoleon_use_rtype to avoid generation of duplicate or redundant return type information.
typehints_defaults (default: None): If None, defaults are not added. Otherwise, adds a default annotation:
- 'comma' adds it after the type, changing Sphinx’ default look to “param (int, default: 1) -- text”.
- 'braces' adds (default: ...) after the type (useful for numpydoc like styles).
- 'braces-after' adds (default: ...) at the end of the parameter documentation text instead.
simplify_optional_unions (default: True): If True, optional parameters of type "Union[...]" are simplified as being of type Union[..., None] in the resulting documentation (e.g. Optional[Union[A, B]] -> Union[A, B, None]). If False, the "Optional"-type is kept. Note: If False, any Union containing None will be displayed as Optional! Note: If an optional parameter has only a single type (e.g Optional[A] or Union[A, None]), it will always be displayed as Optional!
typehints_formatter (default: None): If set to a function, this function will be called with annotation as first argument and sphinx.config.Config argument second. The function is expected to return a string with reStructuredText code or None to fall back to the default formatter.
typehints_use_signature (default: False): If True, typehints for parameters in the signature are shown.
typehints_use_signature_return (default: False): If True, return annotations in the signature are shown.

How it works

The extension listens to the autodoc-process-signature and autodoc-process-docstring Sphinx events. In the former, it strips the annotations from the function signature. In the latter, it injects the appropriate :type argname: and :rtype: directives into the docstring.

Only arguments that have an existing :param: directive in the docstring get their respective :type: directives added. The :rtype: directive is added if and only if no existing :rtype: is found.

Compatibility with sphinx.ext.napoleon

To use sphinx.ext.napoleon with sphinx-autodoc-typehints, make sure you load sphinx.ext.napoleon first, before sphinx-autodoc-typehints. See Issue 15 on the issue tracker for more information.

Dealing with circular imports

Sometimes functions or classes from two different modules need to reference each other in their type annotations. This creates a circular import problem. The solution to this is the following:

Import only the module, not the classes/functions from it
Use forward references in the type annotations (e.g. def methodname(self, param1: 'othermodule.OtherClass'):)

On Python 3.7, you can even use from __future__ import annotations and remove the quotes.