Skip to main content

Python type inferencer

Project description

CI PyPI - Wheel

pytype - 🦆✔

Pytype checks and infers types for your Python code - without requiring type annotations. Pytype can:

  • Lint plain Python code, flagging common mistakes such as misspelled attribute names, incorrect function calls, and much more, even across file boundaries.
  • Enforce user-provided type annotations. While annotations are optional for pytype, it will check and apply them where present.
  • Generate type annotations in standalone files ("pyi files"), which can be merged back into the Python source with a provided merge-pyi tool.

Pytype is a static analyzer; it does not execute the code it runs on.

Thousands of projects at Google rely on pytype to keep their Python code well-typed and error-free.

For more information, check out the user guide, FAQ, or supported features.

How is pytype different from other type checkers?

  1. Pytype uses inference instead of gradual typing. This means it will infer types on code even when the code has no type hints on it. So it can detect issues with code like this, which other type checkers would miss:

    def f():
        return "PyCon"
    def g():
        return f() + 2019
    
    # pytype: line 4, in g: unsupported operand type(s) for +: 'str'
    # and 'int' [unsupported-operands]
    
  2. Pytype is lenient instead of strict. That means it allows all operations that succeed at runtime and don't contradict annotations. For instance, this code will pass as safe in pytype, but fail in other type checkers, which assign types to variables as soon as they are initialized:

    from typing import List
    def get_list() -> List[str]:
        lst = ["PyCon"]
        lst.append(2019)
        return [str(x) for x in lst]
    
    # mypy: line 4: error: Argument 1 to "append" of "list" has
    # incompatible type "int"; expected "str"
    

Also see the corresponding FAQ entry.

Quickstart

To quickly get started with type-checking a file or directory, run the following, replacing file_or_directory with your input:

pip install pytype
pytype file_or_directory

To set up pytype on an entire package, add the following to a setup.cfg file in the directory immediately above the package, replacing package_name with the package name:

[pytype]
inputs = package_name

Now you can run the no-argument command pytype to type-check the package. It's also easy to add pytype to your automated testing; see this example of a GitHub project that runs pytype on Travis.

Finally, pytype generates files of inferred type information, located by default in .pytype/pyi. You can use this information to type-annotate the corresponding source file:

merge-pyi -i <filepath>.py .pytype/pyi/<filename>.pyi

Requirements

You need a Python 3.6-3.8 interpreter to run pytype, as well as an interpreter in $PATH for the Python version of the code you're analyzing (supported: 2.7, 3.5-3.8).

Platform support:

  • Pytype is currently developed and tested on Linux*, which is the main supported platform.
  • Installation on MacOSX requires OSX 10.7 or higher and Xcode v8 or higher.
  • Windows is currently not supported unless you use WSL.

* Note: On Alpine Linux, installing may fail due to issues with upstream dependencies. See the details of this issue for a possible fix.

Installing

Pytype can be installed via pip. Note that the installation requires wheel and setuptools. (If you're working in a virtualenv, these two packages should already be present.)

pip install pytype

Or from the source code on GitHub.

git clone --recurse-submodules https://github.com/google/pytype.git
cd pytype
pip install .

Instead of using --recurse-submodules, you could also have run

git submodule init
git submodule update

in the pytype directory. To edit the code and have your edits tracked live, replace the pip install command with:

pip install -e .

Installing on WSL

Follow the steps above, but make sure you have the correct libraries first:

sudo apt install build-essential python3-dev libpython3-dev

Usage

usage: pytype [options] input [input ...]

positional arguments:
  input                 file or directory to process

Common options:

  • -V, --python-version: Python version (major.minor) of the target code. Defaults to the version that pytype is running under.
  • -o, --output: The directory into which all pytype output goes, including generated .pyi files. Defaults to .pytype.
  • -d, --disable. Comma or space separated list of error names to ignore. Detailed explanations of pytype's error names are in this doc. Defaults to empty.

For a full list of options, run pytype --help.

In addition to the above, you can direct pytype to use a custom typeshed installation instead of its own bundled copy by setting $TYPESHED_HOME.

Config File

For convenience, you can save your pytype configuration in a file. The config file is an INI-style file with a [pytype] section; if an explicit config file is not supplied, pytype will look for a [pytype] section in the first setup.cfg file found by walking upwards from the current working directory.

Start off by generating a sample config file:

$ pytype --generate-config pytype.cfg

Now customize the file based on your local setup, keeping only the sections you need. Directories may be relative to the location of the config file, which is useful if you want to check in the config file as part of your project.

For example, suppose you have the following directory structure and want to analyze package ~/repo1/foo, which depends on package ~/repo2/bar:

~/
├── repo1
│   └── foo
│       ├── __init__.py
│       └── file_to_check.py
└── repo2
    └── bar
        ├── __init__.py
        └── dependency.py

Here is the filled-in config file, which instructs pytype to type-check ~/repo1/foo as Python 3.6 code, look for packages in ~/repo1 and ~/repo2, and ignore attribute errors. Notice that the path to a package does not include the package itself.

$ cat ~/repo1/pytype.cfg

# NOTE: All relative paths are relative to the location of this file.

[pytype]

# Space-separated list of files or directories to process.
inputs =
    foo

# Python version (major.minor) of the target code.
python_version = 3.6

# Paths to source code directories, separated by ':'.
pythonpath =
    .:
    ~/repo2

# Comma or space separated list of error names to ignore.
disable =
    attribute-error

We could've discovered that ~/repo2 needed to be added to the pythonpath by running pytype's broken dependency checker:

$ pytype --config=~/repo1/pytype.cfg ~/repo1/foo/*.py --unresolved

Unresolved dependencies:
  bar.dependency

Subtools

Pytype ships with a few scripts in addition to pytype itself:

  • annotate-ast, an in-progress type annotator for ASTs.
  • merge-pyi, for merging type information from a .pyi file into a Python file.
  • pytd-tool, a parser for .pyi files.
  • pytype-single, a debugging tool for pytype developers, which analyzes a single Python file assuming that .pyi files have already been generated for all of its dependencies.
  • pyxref, a cross references generator.

2021 Roadmap

  • Python 3.9 support
  • Better performance on large files
  • Support for numerical libraries

License

Apache 2.0

Disclaimer

This is not an official Google product.

Project details


Release history Release notifications | RSS feed

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

pytype-2021.3.10.tar.gz (1.9 MB view details)

Uploaded Source

Built Distributions

pytype-2021.3.10-cp38-cp38-manylinux2014_x86_64.whl (1.9 MB view details)

Uploaded CPython 3.8

pytype-2021.3.10-cp38-cp38-macosx_10_14_x86_64.whl (1.9 MB view details)

Uploaded CPython 3.8 macOS 10.14+ x86-64

pytype-2021.3.10-cp37-cp37m-manylinux2014_x86_64.whl (1.9 MB view details)

Uploaded CPython 3.7m

pytype-2021.3.10-cp37-cp37m-macosx_10_14_x86_64.whl (1.9 MB view details)

Uploaded CPython 3.7m macOS 10.14+ x86-64

pytype-2021.3.10-cp36-cp36m-manylinux2014_x86_64.whl (1.9 MB view details)

Uploaded CPython 3.6m

pytype-2021.3.10-cp36-cp36m-macosx_10_14_x86_64.whl (1.9 MB view details)

Uploaded CPython 3.6m macOS 10.14+ x86-64

File details

Details for the file pytype-2021.3.10.tar.gz.

File metadata

  • Download URL: pytype-2021.3.10.tar.gz
  • Upload date:
  • Size: 1.9 MB
  • Tags: Source
  • Uploaded using Trusted Publishing? No
  • Uploaded via: twine/3.3.0 pkginfo/1.7.0 requests/2.25.1 setuptools/54.1.1 requests-toolbelt/0.9.1 tqdm/4.59.0 CPython/3.7.7

File hashes

Hashes for pytype-2021.3.10.tar.gz
Algorithm Hash digest
SHA256 d59e2ba25f53431c3396f019519532e7c3c2a29149494f62d67f2078574ec5e3
MD5 e52c3061c4eaebb50bb88214767d18e6
BLAKE2b-256 0d47bd4f6aaa927c96fb67489b0a28f0541827d2f2125b3b7bce82a21d802572

See more details on using hashes here.

Provenance

File details

Details for the file pytype-2021.3.10-cp38-cp38-manylinux2014_x86_64.whl.

File metadata

  • Download URL: pytype-2021.3.10-cp38-cp38-manylinux2014_x86_64.whl
  • Upload date:
  • Size: 1.9 MB
  • Tags: CPython 3.8
  • Uploaded using Trusted Publishing? No
  • Uploaded via: twine/3.3.0 pkginfo/1.7.0 requests/2.25.1 setuptools/54.1.1 requests-toolbelt/0.9.1 tqdm/4.59.0 CPython/3.7.7

File hashes

Hashes for pytype-2021.3.10-cp38-cp38-manylinux2014_x86_64.whl
Algorithm Hash digest
SHA256 772778051fc43ec53bbb6365049a016b2ea7d4f065f791904cb4a1ca7ed18430
MD5 9aad3d9ca119f3f107f88dfd44553c5c
BLAKE2b-256 c802da31a2b858d329242f3092f339e2513205dff9c6c61d4229e7bd3ab162e0

See more details on using hashes here.

Provenance

File details

Details for the file pytype-2021.3.10-cp38-cp38-macosx_10_14_x86_64.whl.

File metadata

  • Download URL: pytype-2021.3.10-cp38-cp38-macosx_10_14_x86_64.whl
  • Upload date:
  • Size: 1.9 MB
  • Tags: CPython 3.8, macOS 10.14+ x86-64
  • Uploaded using Trusted Publishing? No
  • Uploaded via: twine/3.3.0 pkginfo/1.7.0 requests/2.25.1 setuptools/54.1.1 requests-toolbelt/0.9.1 tqdm/4.59.0 CPython/3.7.7

File hashes

Hashes for pytype-2021.3.10-cp38-cp38-macosx_10_14_x86_64.whl
Algorithm Hash digest
SHA256 af1a9f8d80465fcbb36a5d56843215551a534f0ac71620192c662cfdec58b47d
MD5 067cf806fa4d7a1a2db313bad20d0dfd
BLAKE2b-256 dea0c8b29a6034b8d0d98f514123a69fea3bddc546a86e7e26cde3480adf9585

See more details on using hashes here.

Provenance

File details

Details for the file pytype-2021.3.10-cp37-cp37m-manylinux2014_x86_64.whl.

File metadata

  • Download URL: pytype-2021.3.10-cp37-cp37m-manylinux2014_x86_64.whl
  • Upload date:
  • Size: 1.9 MB
  • Tags: CPython 3.7m
  • Uploaded using Trusted Publishing? No
  • Uploaded via: twine/3.3.0 pkginfo/1.7.0 requests/2.25.1 setuptools/54.1.1 requests-toolbelt/0.9.1 tqdm/4.59.0 CPython/3.7.7

File hashes

Hashes for pytype-2021.3.10-cp37-cp37m-manylinux2014_x86_64.whl
Algorithm Hash digest
SHA256 ceeaa3e445a7acd542b828022a07a0872e68c2de9d5c3dac0e605ac40aadc695
MD5 550f753b09e0d135cb9f3dac77a1afe3
BLAKE2b-256 ceb6125101f5ab46024a089c7bc64762f69bacf68d8a584300cb70ed30aa7178

See more details on using hashes here.

Provenance

File details

Details for the file pytype-2021.3.10-cp37-cp37m-macosx_10_14_x86_64.whl.

File metadata

  • Download URL: pytype-2021.3.10-cp37-cp37m-macosx_10_14_x86_64.whl
  • Upload date:
  • Size: 1.9 MB
  • Tags: CPython 3.7m, macOS 10.14+ x86-64
  • Uploaded using Trusted Publishing? No
  • Uploaded via: twine/3.3.0 pkginfo/1.7.0 requests/2.25.1 setuptools/54.1.1 requests-toolbelt/0.9.1 tqdm/4.59.0 CPython/3.7.7

File hashes

Hashes for pytype-2021.3.10-cp37-cp37m-macosx_10_14_x86_64.whl
Algorithm Hash digest
SHA256 1ad2ff860c70bcf9a1dd5cd8a7829a02d0e64ad410e4667fd8ed4361bb5dd815
MD5 30405115adcb896f245acb6e0a98878b
BLAKE2b-256 85ec02f7d097fc39178040f5e77b4f771b209556e776806b2216dc1f4f48bd58

See more details on using hashes here.

Provenance

File details

Details for the file pytype-2021.3.10-cp36-cp36m-manylinux2014_x86_64.whl.

File metadata

  • Download URL: pytype-2021.3.10-cp36-cp36m-manylinux2014_x86_64.whl
  • Upload date:
  • Size: 1.9 MB
  • Tags: CPython 3.6m
  • Uploaded using Trusted Publishing? No
  • Uploaded via: twine/3.3.0 pkginfo/1.7.0 requests/2.25.1 setuptools/54.1.1 requests-toolbelt/0.9.1 tqdm/4.59.0 CPython/3.7.7

File hashes

Hashes for pytype-2021.3.10-cp36-cp36m-manylinux2014_x86_64.whl
Algorithm Hash digest
SHA256 f20f20e52a26e0ea067baac76a67f751f4574f1fd1b96654994258afabb8c33f
MD5 b65454fcdb068ed27d22433146087872
BLAKE2b-256 fd37b1739e72925bf05c4f4e6d2c446072e991263a196d900505200dd70b5747

See more details on using hashes here.

Provenance

File details

Details for the file pytype-2021.3.10-cp36-cp36m-macosx_10_14_x86_64.whl.

File metadata

  • Download URL: pytype-2021.3.10-cp36-cp36m-macosx_10_14_x86_64.whl
  • Upload date:
  • Size: 1.9 MB
  • Tags: CPython 3.6m, macOS 10.14+ x86-64
  • Uploaded using Trusted Publishing? No
  • Uploaded via: twine/3.3.0 pkginfo/1.7.0 requests/2.25.1 setuptools/54.1.1 requests-toolbelt/0.9.1 tqdm/4.59.0 CPython/3.7.7

File hashes

Hashes for pytype-2021.3.10-cp36-cp36m-macosx_10_14_x86_64.whl
Algorithm Hash digest
SHA256 637a976515ffb08e15df06ea4623cb95130dd120be0cf4dedcd28b9e28bd9e92
MD5 53089d32ccd097e44affd3fc9109f975
BLAKE2b-256 d6bfb9247658ac0916b6db4fb1c97053f0056ccee4d95c944a9a11c23597019c

See more details on using hashes here.

Provenance

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page