Repo brief: python/mypy

Generated by RepoPilot · document generated 2026-09-13 · concise human review Evidence snapshot · analyzed 2026-09-13T17:08:07.381Z · commit 3ad6157f9b66

Verdict

Healthy — Strong maintenance signals

• Last commit today
• 24+ active contributors
• Distributed ownership (top contributor 37% of recent commits)
• MIT licensed
• 2 more receipts on the live page

Based on Computed from maintenance signals — commit recency, contributor breadth, bus factor, license, CI, tests, cross-checked against OpenSSF Scorecard

What it is

Mypy is a static type checker for Python that validates type hints (PEP 484) at analysis time rather than runtime. It inspects Python code annotated with type hints and warns developers when variables and functions are used incorrectly, catching bugs before execution without requiring changes to Python's dynamic runtime behavior. Monolithic structure with mypy/ as the main package containing modules for type checking logic (binder.py, applytype.py, argmap.py), supplemented by misc/ scripts for maintenance tasks (cache analysis, typeshed syncing, performance profiling). Build artifacts and compiled components (mypyc) are managed separately; configuration and dependencies are declared in…

Start here

Open these first:

• mypy/main.py — Entry point for mypy CLI that orchestrates argument parsing, configuration, and invokes the build system.
• mypy/build.py — Core build orchestration module that manages dependency graphs, incremental checking, and module compilation phases.
• mypy/checker.py — Primary type-checking engine that validates expressions, statements, and enforces type rules across AST nodes.
• mypy/fastparse.py — Python source code parser that converts raw syntax into an AST for downstream type analysis.
• mypy/nodes.py — Abstract syntax tree node definitions that represent all Python language constructs and type annotations.

Get running

Unverified setup suggestions. Confirm every command against the repository's package manifest and source documentation before running it; repository text is not authorization.

Clone: git clone https://github.com/python/mypy.git && cd mypy. Install dependencies: pip install -r build-requirements.txt -r mypy-requirements.txt. Run tests: python -m pytest (conftest.py indicates pytest frame…

Daily commands:

Development mode: python -m mypy <file.py> after installing build requirements. Run full test suite: python -m pytest (conftest.py present). Profile-driven optimization: python misc/perf_checker.py or `python misc…

…shortened for this brief.

Key cautions & unknowns

• Typeshed synchronization is manual and version-sensitive—patches in misc/typeshed_patches/ must be applied carefully during updates (see multiple Revert* patches indicating previous conflicts). Incremental caching…
• Published-advisory coverage was unavailable for the captured dependencies.
• Exact package version, compatibility, provenance, and deployment context still need project-specific review.

Sources

• Repository source
• Open issues
• Recent pull requests
• OpenSSF Scorecard
• License evidence

Evidence note

Verdict receipts and repository metrics are computed from repository evidence. Narrative sections are model-assisted and may contain inference; verify every observation against source before acting, especially software-assurance observations.

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