python_lint_fix

Python Lint Fix

Analyze Python files for lint violations, type errors, and security issues using ruff, mypy, and bandit. Automatically fix what can be fixed and explain remaining issues.

When to Use

• You want to check Python files for code quality issues before committing
• You need to find and fix lint violations, type errors, or security issues
• You want to auto-fix formatting and import sorting with ruff
• You are reviewing Python code and want a quick quality check

Prerequisites

The following tools must be installed. If missing, install them with:

uv pip install ruff mypy bandit

• ruff -- fast Python linter and formatter
• mypy -- static type checker for Python
• bandit -- security-focused static analysis tool

Workflow

1. Identify target files -- determine which Python files to check. Use changed files from git or user-specified paths:

   git diff --name-only HEAD -- '*.py'
   

   If the user specifies files or directories, use those instead.

2. Run ruff check on the target files and capture the output:

   ruff check <files>
   

3. Run mypy on the target files and capture the output:

   mypy <files>
   

4. Run bandit on the target files and capture the output:

   bandit -r <files>
   

5. Present findings grouped by tool. For each issue, include:

   • File path and line number (file:line)
   • Rule ID (e.g., E501, F841, B101)
   • Severity (error, warning, info)
   • Explanation of what the rule catches and why it matters

6. Offer to auto-fix issues that ruff can handle automatically:

   ruff check --fix <files>
   ruff format <files>
   

7. Re-run checks to confirm fixes were applied and report any remaining issues:

   ruff check <files>
   mypy <files>
   bandit -r <files>
   

Troubleshooting

Problem	Cause	Solution
ruff: command not found	ruff is not installed	Run uv pip install ruff or pip install ruff
mypy: command not found	mypy is not installed	Run uv pip install mypy or pip install mypy
bandit: command not found	bandit is not installed	Run uv pip install bandit or pip install bandit
mypy reports Cannot find implementation or library stub	Missing type stubs for third-party packages	Run mypy --install-types or add stubs with uv pip install types-<package>
mypy reports Skipping analyzing	Module is not in the mypy search path	Add the source directory to mypy.ini or pyproject.toml under [tool.mypy] with mypy_path
ruff ignores some files	Files are excluded in pyproject.toml or ruff.toml	Check [tool.ruff] exclude patterns in your config file
Too many issues reported	No config file limiting rule set	Create a ruff.toml or [tool.ruff] section in pyproject.toml to select specific rule sets
bandit reports false positives	Some rules are too strict for your codebase	Use # nosec inline comments or configure exclusions in .bandit or pyproject.toml
ruff check --fix did not fix all issues	Some violations require manual intervention	Review the remaining issues and fix them by hand; ruff marks auto-fixable rules in its output