sphinx-autodoc-typehints

This extension allows you to use Python 3 annotations for documenting acceptable argument types and return value types of functions. 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 '{} {}'.format(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 '{} {}'.format(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:

set_type_checking_flag (default: False): if True, set typing.TYPE_CHECKING to True to enable "expensive" typing imports
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.
typehints_document_rtype (default: True): If False, never add an :rtype: directive. If True, add the :rtype: directive if no existing :rtype: is found.

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.

Using type hint comments

If you're documenting code that needs to stay compatible with Python 2.7, you cannot use regular type annotations. Instead, you must either be using Python 3.8 or later or have typed_ast installed. The package extras type_comments will pull in the appropiate dependencies automatically. Then you can add type hint comments in the following manner:

def myfunction(arg1, arg2):
    # type: (int, str) -> int
    return 42

or alternatively:

def myfunction(
    arg1,  # type: int
    arg2  # type: str
):
    # type: (...) -> int
    return 42