{"id":5040,"library":"pytype","title":"Pytype","description":"Pytype is a static type analyzer for Python that infers and checks types in Python code, even without explicit type annotations. It can lint plain Python code for common mistakes, enforce user-provided type annotations, and generate `.pyi` stub files. Developed by Google, Pytype is currently in maintenance mode, with Python 3.12 being the last officially supported version, focusing on bugfixes rather than new features.","status":"maintenance","version":"2024.10.11","language":"en","source_language":"en","source_url":"https://github.com/google/pytype","tags":["static analysis","type checking","type inference","python","tool","linter"],"install":[{"cmd":"pip install pytype","lang":"bash","label":"Install Pytype"}],"dependencies":[{"reason":"Required for installation, especially outside a virtual environment or from source.","package":"wheel","optional":true},{"reason":"Required for installation, especially outside a virtual environment or from source.","package":"setuptools","optional":true},{"reason":"Required for installation on Linux-based systems.","package":"build-essential","optional":true},{"reason":"Required for installation on Linux-based systems.","package":"python3-dev","optional":true},{"reason":"Required for installation on Linux-based systems.","package":"libpython3-dev","optional":true}],"imports":[],"quickstart":{"code":"# To check a single file or directory:\n# pytype my_module.py\n# pytype my_package/\n\n# For package-wide configuration using pyproject.toml:\n# 1. Create a pyproject.toml in your project root with the following:\n# [tool.pytype]\n# inputs = ['your_package_name']\n\n# 2. Then run pytype without arguments:\n# pytype\n\n# Example Python file (example.py):\ndef greet(name):\n    return \"Hello, \" + name\n\ndef add(a, b):\n    return a + b\n\n# Run pytype on this file from your terminal:\n# pytype example.py\n# Expected output for add function (e.g., if you call add(1, '2')):\n# File \"example.py\", line 5, in add: unsupported operand type(s) for +: 'int' and 'str' [unsupported-operands]","lang":"bash","description":"Pytype is primarily a command-line tool. To quickly get started, run `pytype` followed by the file or directory you wish to analyze. For project-level configuration, use a `pyproject.toml` file to specify inputs and settings."},"warnings":[{"fix":"Consider migrating to actively developed type checkers if you need support for newer Python versions or actively evolving typing features.","message":"Pytype is in maintenance mode; Google has discontinued active development, and Python 3.12 is the last supported version. No new features will be added, only bugfixes. Users are encouraged to explore alternative type checkers like Mypy, Pyright, ty, or Pyrefly.","severity":"breaking","affected_versions":"All versions beyond Python 3.12 runtime environment."},{"fix":"Be aware of Pytype's leniency. If stricter checking is desired, review Pytype's error classes and configuration options, or consider a different type checker.","message":"Pytype's default behavior is lenient compared to other type checkers like Mypy. It allows operations that succeed at runtime and don't contradict annotations, which might lead to different results, particularly with container types or `Optional` handling.","severity":"gotcha","affected_versions":"All"},{"fix":"Use inline directives like `# pytype: disable=attribute-error` or `# type: ignore` for specific suppression. Consult the error classes documentation for precise error names.","message":"For silencing specific errors, use `pytype: disable=error-class` on the line or block, or `type: ignore`. Disabling errors for an entire file can be done by placing a disable directive on its own line at the start of the file.","severity":"gotcha","affected_versions":"All"},{"fix":"Split large files into smaller modules. Add explicit type annotations to function parameters and return types. Simplify complex variable initializations or union types.","message":"Performance can degrade significantly on very large Python files (anecdotally, over ~1500 lines). Extensive inference on complex, unannotated code can be slow.","severity":"gotcha","affected_versions":"All"},{"fix":"Avoid experimental Pytype-specific annotations in code intended for wider compatibility or analysis by other type checkers.","message":"Some experimental features, such as `...` as a top-level annotation for 'inferred type', are unique to Pytype and not supported by other type checkers (e.g., Mypy, Pyright). Using these can lead to errors when analyzing code with other tools.","severity":"gotcha","affected_versions":"All"},{"fix":"For Windows users, it is recommended to run Pytype within a WSL environment.","message":"Pytype is primarily developed and tested on Linux. While it supports macOS (10.7+ and Xcode 8+), Windows support typically requires the Windows Subsystem for Linux (WSL).","severity":"gotcha","affected_versions":"All"}],"env_vars":null,"last_verified":"2026-04-12T00:00:00.000Z","next_check":"2026-07-11T00:00:00.000Z"}