Pyrefly

Pyrefly is a type checker and language server for Python, which provides lightning-fast type checking along with IDE features such as code navigation, semantic highlighting, and code completion. It is available as a command-line tool and a VSCode extension.

Key features:

• Type Inference: Pyrefly infers types in most locations, apart from function parameters. It can infer types of variables and return types.
• Flow Types: Pyrefly can understand your program's control flow to refine static types.
• Incrementality: Pyrefly aims for large-scale incrementality at the module level, with optimized checking and parallelism.