Python Review

Python review guidelines

This project uses Python for the SDK (python/cog/) which defines the predictor interface, type system, and HTTP/queue server.

What linters already catch (skip these)

ruff handles pycodestyle (E), Pyflakes (F), isort (I), warnings (W), bandit (S), bugbear (B), and annotations (ANN). Don't flag issues these would catch.

What to look for

Type annotations

• Required on all function signatures
• Use typing_extensions for backward compatibility
• Avoid Any where a concrete type is possible
• Check that type annotations actually match runtime behavior

Compatibility

• Must support Python 3.10 through 3.13
• Watch for syntax/stdlib features only available in newer versions
• from __future__ import annotations if using newer annotation syntax

Error handling

• No bare except: or except Exception: that swallows everything
• Exceptions should have descriptive messages
• Resource cleanup with context managers, not try/finally when avoidable

Async patterns

• Tests use pytest-asyncio -- async tests need proper fixtures
• Watch for blocking calls inside async functions
• Proper cleanup of async resources (aclose, async context managers)

Predictor interface

• base_predictor.py is the core interface -- changes here affect all users
• types.py defines input/output types -- check backward compatibility
• Server code in python/cog/server/ handles HTTP -- watch for request handling bugs

Testing

• Uses pytest with fixtures
• tox runs tests across Python 3.10-3.13
• Test isolation: don't rely on global state or test ordering

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