Prevent Exception Handling AntiPatterns in Python

Inspired by this blog post. I described the building process of this tool here.

“For those who like dinosaurs 🦖 and clean try/except ✨ blocks.”

Summary

• Installation and usage
  • Installation
  • Usage
  • flake8 Plugin
• Violations
  • Autofix support
  • Ignoring violations
  • Configuration
• Pre-commit
• Show your style
• Extra Resources
• Contributing
• Change log
• License
• Credits

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Installation and usage

Installation

pip install tryceratops

OR

poetry add -D tryceratops

Usage

tryceratops [filename or dir...]

You can enable experimental analyzers by running:

tryceratops --experimental [filename or dir...]

You can ignore specific violations by using: --ignore TRYXXX repeatedly:

tryceratops --ignore TRY201 --ignore TRY202 [filename or dir...]

You can exclude dirs by using: --exclude dir/path repeatedly:

tryceratops --exclude tests --exclude .venv [filename or dir...]

You can also autofix some violations:

tryceratops --autofix [filename or dir...]

flake8 Plugin

🦖 Tryceratops is also a plugin for flake8, so you can:

❯ flake8 --select TRY src/tests/samples/violations/call_raise_vanilla.py
src/tests/samples/violations/call_raise_vanilla.py:13:9: TRY002 Create your own exception
src/tests/samples/violations/call_raise_vanilla.py:13:9: TRY003 Avoid specifying long messages outside the exception class
src/tests/samples/violations/call_raise_vanilla.py:21:9: TRY201 Simply use 'raise' without specifying exception object again

Violations

All violations and its descriptions can be found in docs.

Autofix support

So far, autofix only supports violations: TRY200, TRY201, and TRY400.

Ignoring violations

If you want to ignore a violation in a specific file, you can either:

• Add a comment with noqa to the top of the file you want to ignore
• Add a comment with noqa to the line you want to ignore
• Add a comment with noqa: CODE to the line you want to ignore a specific violation

Example:

def verbose_reraise_1():
    try:
        a = 1
    except Exception as ex:
        raise ex  # noqa: TRY202

Configuration

You can set up a pyproject.toml file to set rules. This is useful to avoid reusing the same CLI flags over and over again and helps to define the structure of your project.

Example:

[tool.tryceratops]
exclude = ["samples"]
ignore = ["TRY002", "TRY200", "TRY300"]
experimental = false
check_pickable = false
allowed_base_exceptions = ["MyAppBase"]

CLI flags always overwrite the config file.

Pre-commit

If you wish to use pre-commit, add this:

  - repo: https://github.com/guilatrova/tryceratops
    rev: v2.4.1
    hooks:
      - id: tryceratops

Show your style

Add this fancy badge to your project's README.md:

[![try/except style: tryceratops](https://img.shields.io/badge/try%2Fexcept%20style-tryceratops%20%F0%9F%A6%96%E2%9C%A8-black)](https://github.com/guilatrova/tryceratops)

Extra Resources

If you want to read more about:

• How to structure exceptions in Python 🐍 🏗️ 💣
• How to log in Python 🐍🌴
• Book: Effective Python

Contributing

Thank you for considering making Tryceratops better for everyone!

Refer to Contributing docs.

Change log

See CHANGELOG.

License

MIT

Credits

Thanks to God for the inspiration 🙌 ☁️ ☀️

The black project for insights.