flake8

Flake8 is a Python linting tool that combines the functionality of PyFlakes, pycodestyle (formerly pep8), and the McCabe complexity checker to detect potential errors and enforce coding standards. It analyzes Python source files to flag syntax errors, undefined names, unused imports, and style violations, providing a single, extensible interface for several quality checks.

It is installed via Python's package manager and run from the command line as flake8. It reports errors using codes drawn from its component tools: F codes from PyFlakes, E and W codes from PyCodeStyle, and C codes for complexity. Flake8 can be integrated into editors, IDEs, and continuous integration systems, and is configurable through configuration files such as .flake8, setup.cfg, tox.ini, or pyproject.toml. Common options control the maximum line length, exclusion of files, per-file ignores, and the maximum allowed complexity. The tool supports a plugin system; additional checks such as naming conventions or project-specific rules can be added via installed plugins.

Flake8 is open-source software distributed under the MIT license and maintained by a community of volunteers. It is widely used in Python projects to maintain consistent style and quality, and benefits from ongoing contributions and ecosystem plugins that extend its functionality.