Type engine
PyCharm relies on a type engine to power code insight features that depend on type information, including:
Type inference
Type-related diagnostics and inspections
Quick documentation
Inlay hints for inferred types
Code completion suggestions based on inferred types
By default, PyCharm uses its built-in type engine. You can also switch to an external type engine to delegate type analysis to a dedicated tool optimized for large Python codebases.
Built-in type engine
The built-in type engine analyzes your code based on type hints (PEP 484), type comments, stubs, and docstrings, combined with PyCharm's own type inference for unannotated code. It works out of the box without additional setup and supports all interpreter configurations, including local, virtual, Docker, Docker Compose, WSL, SSH, and multi-module projects.
External type engine
An external type engine is a third-party type checker that PyCharm delegates type analysis to. Once enabled, the external engine powers type inference, type-related diagnostics, quick documentation, and inlay hints in the editor, replacing the built-in type engine for these features.
Pyrefly
Pyrefly is a next-generation Python type checker written in Rust. As an external type engine, Pyrefly significantly speeds up PyCharm's code insight features on large projects.
Switch to Pyrefly as the type engine
Click the Type widget in the status bar. By default, the widget indicates that the built-in type engine is in use.
Select Pyrefly from the list. If Pyrefly isn't installed yet, PyCharm installs it automatically.
Once Pyrefly is active, the Pyrefly icon appears in the status bar. Hover over the icon to check the version being used.
You can configure Pyrefly settings such as the executable location or enabled features in .