Automatic stub generation (stubgen)

A stub file (see PEP 484) contains only type hints for the public interface of a module, with empty function bodies. Mypy can use a stub file instead of the real implementation to provide type information for the module. They are useful for third-party modules whose authors have not yet added type hints (and when no stubs are available in typeshed) and C extension modules (which mypy can’t directly process).

Mypy includes the stubgen tool that can automatically generate stub files (.pyi files) for Python modules and C extension modules. For example, consider this source file:

from other_module import dynamic

BORDER_WIDTH = 15

class Window:
    parent = dynamic()
    def __init__(self, width, height):
        self.width = width
        self.height = height

def create_empty() -> Window:
    return Window(0, 0)

Stubgen can generate this stub file based on the above file:

from typing import Any

BORDER_WIDTH: int = ...

class Window:
    parent: Any = ...
    width: Any = ...
    height: Any = ...
    def __init__(self, width, height) -> None: ...

def create_empty() -> Window: ...

Stubgen generates draft stubs. The auto-generated stub files often require some manual updates, and most types will default to Any. The stubs will be much more useful if you add more precise type annotations, at least for the most commonly used functionality.

The rest of this section documents the command line interface of stubgen. Run stubgen --help for a quick summary of options.

Note

The command-line flags may change between releases.

Specifying what to stub

You can give stubgen paths of the source files for which you want to generate stubs:

$ stubgen foo.py bar.py

This generates stubs out/foo.pyi and out/bar.pyi. The default output directory out can be overridden with -o DIR.

You can also pass directories, and stubgen will recursively search them for any .py files and generate stubs for all of them:

$ stubgen my_pkg_dir

Alternatively, you can give module or package names using the -m or -p options:

$ stubgen -m foo -m bar -p my_pkg_dir

Details of the options:

-m MODULE, --module MODULE

Generate a stub file for the given module. This flag may be repeated multiple times.

Stubgen will not recursively generate stubs for any submodules of the provided module.

-p PACKAGE, --package PACKAGE

Generate stubs for the given package. This flag maybe repeated multiple times.

Stubgen will recursively generate stubs for all submodules of the provided package. This flag is identical to --module apart from this behavior.

Note

You can’t mix paths and -m/-p options in the same stubgen invocation.

Stubgen applies heuristics to avoid generating stubs for submodules that include tests or vendored third-party packages.

Specifying how to generate stubs

By default stubgen will try to import the target modules and packages. This allows stubgen to use runtime introspection to generate stubs for C extension modules and to improve the quality of the generated stubs. By default, stubgen will also use mypy to perform light-weight semantic analysis of any Python modules. Use the following flags to alter the default behavior:

--no-import

Don’t try to import modules. Instead only use mypy’s normal search mechanism to find sources. This does not support C extension modules. This flag also disables runtime introspection functionality, which mypy uses to find the value of __all__. As result the set of exported imported names in stubs may be incomplete. This flag is generally only useful when importing a module causes unwanted side effects, such as the running of tests. Stubgen tries to skip test modules even without this option, but this does not always work.

--parse-only

Don’t perform semantic analysis of source files. This may generate worse stubs – in particular, some module, class, and function aliases may be represented as variables with the Any type. This is generally only useful if semantic analysis causes a critical mypy error.

--doc-dir PATH

Try to infer better signatures by parsing .rst documentation in PATH. This may result in better stubs, but currently it only works for C extension modules.

Additional flags

--py2

Run stubgen in Python 2 mode (the default is Python 3 mode).

--ignore-errors

If an exception was raised during stub generation, continue to process any remaining modules instead of immediately failing with an error.

--include-private

Include definitions that are considered private in stubs (with names such as _foo with single leading underscore and no trailing underscores).

--export-less

Don’t export all names imported from other modules within the same package. Instead, only export imported names that are not referenced in the module that contains the import.

--search-path PATH

Specify module search directories, separated by colons (only used if --no-import is given).

--python-executable PATH

Use Python interpreter at PATH for importing modules and runtime introspection. This has no effect with --no-import, and this only works in Python 2 mode. In Python 3 mode the Python interpreter used to run stubgen will always be used.

-o PATH, --output PATH

Change the output directory. By default the stubs are written in the ./out directory. The output directory will be created if it doesn’t exist. Existing stubs in the output directory will be overwritten without warning.

-v, --verbose

Produce more verbose output.

-q, --quiet

Produce less verbose output.