Python Type Checker Comparison: Empty Container Inference

2026-03-02

Python type checkers handle empty containers using three strategies: infer Any (permissive but unsafe), infer from all usages (accurate but errors may appear far from the bug), or infer from the first usage (more actionable but sometimes wrong). Each approach balances type safety, performance, and error clarity, with Pyrefly defaulting to first-use inference for more actionable errors.