pytest-monkeytype

pytest-monkeytype is a pytest plugin that integrates MonkeyType, Instagram's runtime type collection system, into the pytest testing framework. It enables developers to automatically generate Python type annotations by capturing type information while tests run, significantly reducing the manual effort required to add type hints to existing codebases.

Key Features

• Runtime Type Collection — Captures argument and return value types during test execution and stores them in a SQLite database.
• Annotation Generation — Uses MonkeyType to generate type stub files or directly apply annotations to source code based on collected data.
• Seamless Integration — Works as a standard pytest plugin, requiring only a command-line flag to activate type collection.
• Flexible Output — Supports generating type stubs for review or applying annotations automatically to modules.

Philosophy

The plugin follows a pragmatic approach to type annotation, believing that types should be inferred from actual runtime behavior rather than manually specified, making it easier to adopt type hints in large, untyped codebases.