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
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.
stubgen --help for a quick summary of options.
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/bar.pyi. The default
out can be overridden with
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
$ stubgen -m foo -m bar -p my_pkg_dir
Details of the options:
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.
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
--moduleapart from this behavior.
You can’t mix paths and
-p options in the same stubgen
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:
- Don’t try to import modules. Instead 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 generates an error for some reason.
- 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
Anytype. This is generally only useful if semantic analysis causes a critical mypy error.
- 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.
- Run stubgen in Python 2 mode (the default is Python 3 mode).
- If an exception was raised during stub generation, continue to process any remaining modules instead of immediately failing with an error.
- Include definitions that are considered private in stubs (with names such
_foowith single leading underscore and no trailing underscores).
- Specify module search directories, separated by colons (only used if
- Use Python interpreter at
PATHfor 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.
- Change the output directory. By default the stubs are written in the
./outdirectory. The output directory will be created if it doesn’t exist. Existing stubs in the output directory will be overwritten without warning.