python ยท diff
git:20260703.3e63b47 to git:20261005.01a86d1
9 added, 9 removed. Audit A to A.
---
name: python
description: Write clean, readable Pythonic code. Use this skill any time you write or change a Python file.
---
# General guidelines
# Coding Style
- Always write clean, readable, well separated, well organized, Pythonic code.
- Don't run linters or formatters, they will run automatically after every edit by the harness.
- When using `datetime`, import it like this: `import datetime as dt`
- CRITICAL: ALWAYS put ALL imports at the top of the file, NEVER inside
functions, methods, or any other block. No exceptions. Use `TYPE_CHECKING` guard
for type-only imports to avoid circular dependencies.
# Type hints
- - ALWAYS type hint every function and method signature precisely even in tests.
- - NEVER write "-> None" type hint for return values, they are not necessary.
+ - ALWAYS type hint every function and method signature precisely even in tests, except for the return value `None`,
+ they are not necessary (`-> None:`)
- No need to type hint variables from functions call return values inside function bodies, they are inferred from the method return type,
except extreme cases when the type is a huge help or a generic and it's concrete type cannot be determined.
- Only use APIs, class names, variables or objects which you already read or know exist for sure.
- Use the new pipe operator for `Optional` variables like this: `value | None`
- - Use `Any` for "all types" instead of `object`.
+ - When necessary, use `Any` for "all types" instead of `object`, but only as a last resort or when that's the actual type used.
# Testing
- ALWAYS use `pytest` for all tests
- - ALWAYS assert on whole ouptut or full results in tests, not just tiny parts
+ - ALWAYS assert on whole ouptut or full results in tests, not just tiny parts.
- For mocking, use pytest `monkeypatch` fixture, NEVER `unittest.mock` and NEVER
any of the `Mock` classes or `patch` function
- IMPORTANT: NEVER import from `conftest.py`
- - ALWAYS type hint test function parameters correctly.
+ - ALWAYS type hint test function parameters correctly, except for `-> None:`.
- Don't make a test class with only one function, a module-level test function is enough
- - NEVER use `unittest.mock` or any of the `Mock` classes or `patch` function, never assert on method calls,
- use real objects and assert on full results. When absolutely necessary and can't be avoided, use `pytest.monkeypatch`,
- when the test setup would be too difficult or the code have side effects, but consider writing a fake.
- - ALWAYS assert on the full result of the function call, never just list lengths or containment, except where that's the point.
+ - Don't assert on method calls, use real objects and assert on full results. When this is absolutely necessary and can't be avoided,
+ use `pytest.monkeypatch`, when the test setup would be too difficult or the code have side effects, but consider writing a fake.
+ - Never just list lengths or containment, except where that's the point.
+ - Don't put if statements in tests dependding on test case, those are probably belong to two separate test cases.
# Managing dependencies
- Use `uv add` for adding dependencies, never directly edit `pyproject.toml` files.
- For CLI scripts and apps, ALWAYS use `click` library instead of `argparse`, add it to dependencies if necessary.