typeshed

About

Typeshed contains external type annotations for the Python standard library and Python builtins, as well as third party packages as contributed by people external to those projects.

This data can e.g. be used for static analysis, type checking or type inference.

For information on how to use typeshed, read below. Information for contributors can be found in CONTRIBUTING.md. Please read it before submitting pull requests; do not report issues with annotations to the project the stubs are for, but instead report them here to typeshed.

Typeshed supports Python versions 2.7 and 3.6 and up.

Using

If you're just using mypy (or pytype or PyCharm), as opposed to developing it, you don't need to interact with the typeshed repo at all: a copy of typeshed is bundled with mypy.

When you use a checked-out clone of the mypy repo, a copy of typeshed should be included as a submodule, using

$ git clone --recurse-submodules https://github.com/python/mypy.git

or

$ git clone https://github.com/python/mypy.git
$ cd mypy
$ git submodule init
$ git submodule update

and occasionally you will have to repeat the final command (git submodule update) to pull in changes made in the upstream typeshed repo.

PyCharm and pytype similarly include a copy of typeshed. The one in pytype can be updated in the same way if you are working with the pytype repo.

Format

Each Python module is represented by a .pyi "stub file". This is a syntactically valid Python file, although it usually cannot be run by Python 3 (since forward references don't require string quotes). All the methods are empty.

Python function annotations (PEP 3107) are used to describe the signature of each function or method.

See PEP 484 for the exact syntax of the stub files and CONTRIBUTING.md for the coding style used in typeshed.

Directory structure

stdlib

This contains stubs for modules the Python standard library -- which includes pure Python modules, dynamically loaded extension modules, hard-linked extension modules, and the builtins.

third_party

Modules that are not shipped with Python but have a type description in Python go into third_party. Since these modules can behave differently for different versions of Python, third_party has version subdirectories, just like stdlib.

For more information on directory structure and stub versioning, see the relevant section of CONTRIBUTING.md.

Third-party packages are generally removed from typeshed when one of the following criteria is met:

• The upstream package ships a py.typed file for at least 6-12 months, or
• the package does not support any of the Python versions supported by typeshed.

Contributing

Please read CONTRIBUTING.md before submitting pull requests. If you have questions related to contributing, drop by the typing Gitter.

Running the tests

The tests are automatically run on every PR and push to the repo.

There are several tests:

• tests/mypy_test.py tests typeshed with mypy
• tests/pytype_test.py tests typeshed with pytype.
• tests/mypy_self_check.py checks mypy's code base using this version of typeshed.
• tests/mypy_test_suite.py runs a subset of mypy's test suite using this version of typeshed.
• tests/check_consistent.py checks certain files in typeshed remain consistent with each other.
• tests/stubtest_test.py checks stubs against the objects at runtime.
• flake8 enforces a style guide.

Setup

Run:

$ python3.6 -m venv .venv3
$ source .venv3/bin/activate
(.venv3)$ pip install -U pip
(.venv3)$ pip install -r requirements-tests-py3.txt

This will install mypy (you need the latest master branch from GitHub), typed-ast, flake8 (and plugins), pytype, black and isort.

mypy_test.py

This test requires Python 3.6 or higher; Python 3.6.1 or higher is recommended. Run using:(.venv3)$ python3 tests/mypy_test.py

This test is shallow — it verifies that all stubs can be imported but doesn't check whether stubs match their implementation (in the Python standard library or a third-party package). It has an exclude list of modules that are not tested at all, which also lives in the tests directory.

If you are in the typeshed repo that is submodule of the mypy repo (so .. refers to the mypy repo), there's a shortcut to run the mypy tests that avoids installing mypy:

$ PYTHONPATH=../.. python3 tests/mypy_test.py

You can restrict mypy tests to a single version by passing -p2 or -p3.9:

$ PYTHONPATH=../.. python3 tests/mypy_test.py -p3.9
running mypy --python-version 3.9 --strict-optional # with 342 files

pytype_test.py

This test requires Python 2.7 and Python 3.6. Pytype will find these automatically if they're in PATH, but otherwise you must point to them with the --python27-exe and --python36-exe arguments, respectively. Run using: (.venv3)$ python3 tests/pytype_test.py

This test works similarly to mypy_test.py, except it uses pytype.

mypy_self_check.py

This test requires Python 3.6 or higher; Python 3.6.1 or higher is recommended. Run using: (.venv3)$ python3 tests/mypy_self_check.py

This test checks mypy's code base using mypy and typeshed code in this repo.

mypy_test_suite.py

This test requires Python 3.5 or higher; Python 3.6.1 or higher is recommended. Run using: (.venv3)$ python3 tests/mypy_test_suite.py

This test runs mypy's own test suite using the typeshed code in your repo. This will sometimes catch issues with incorrectly typed stubs, but is much slower than the other tests.

check_consistent.py

Run using: python3 tests/check_consistent.py

stubtest_test.py

This test requires Python 3.6 or higher. Run using (.venv3)$ python3 tests/stubtest_test.py

This test compares the stdlib stubs against the objects at runtime. Because of this, the output depends on which version of Python and on what kind of system it is run. Thus the easiest way to run this test is via Github Actions on your fork; if you run it locally, it'll likely complain about system-specific differences (in e.g, socket) that the type system cannot capture. If you need a specific version of Python to repro a CI failure, pyenv can help.

Due to its dynamic nature, you may run into false positives. In this case, you can add to the whitelists for each affected Python version in tests/stubtest_whitelists. Please file issues for stubtest false positives at mypy.

To run stubtest against third party stubs, it's easiest to use stubtest directly, with (.venv3)$ python3 -m mypy.stubtest --custom-typeshed-dir <path-to-typeshed> <third-party-module>. stubtest can also help you find things missing from the stubs.

flake8

flake8 requires Python 3.6 or higher. Run using: (.venv3)$ flake8

Note typeshed uses the flake8-pyi and flake8-bugbear plugins.