:github_badge:`quantifiedcode/python-anti-patterns`

Welcome, fellow Pythoneer! This is a small book of Python anti-patterns and worst practices.

Learning about these anti-patterns will help you to avoid them in your own code and make you a better programmer (hopefully). Each pattern comes with a small description, examples and possible solutions.

Short answer: We think that you can learn as much from reading bad code as you can from reading good one.

Long answer: There is an overwhelming amount of Python books that show you how to do things by focusing on best practices and examples of good code. There are only very few books out there that show you how not to do things. We wanted to change that by providing you with an anti-book that teaches you things which you should never do in practice.

We're QuantifiedCode, a Berlin-based startup. Our mission is to help programmers write better code! Our first product is an online tool for automated, data-driven code review. When building this tool we learned a lot about code quality in Python and decided to compile our knowledge into this book.

We tried to categorize each anti-patterns into one of the following categories:

• Correctness: Anti-patterns that will literally break your code or make it do the wrong things.
• Maintainability: Anti-patterns that will make your code hard to maintain or extend.
• Readability: Anti-patterns that will make your code hard to read or understand.
• Performance: Anti-patterns that will unnecessarily slow your code down.
• Security: Anti-patterns that will pose a security risk to your program.

Many of the patterns do of course belong in more than one of these categories, so please don't take the choice that we've made too serious. If you think a pattern is grossly misplaced in its category, feel free to create an issue on Github.

Whenever we cite an anti-pattern from another source we tried including the link to the original article on the bottom of the page. If you should have missed one, please feel free to add it and make a pull request on Github. Thanks!

This document is licensed under a creative-commons NC license, so you can use the text freely for non-commercial purposes and adapt it to your needs. The only thing we ask in return is the inclusion of a link to this page on the top of your website, so that your readers will be able to find the content in its original form and possibly even contribute to it.

If you think this collection can be improved or extended, please contribute! You can do this by simply forking our Github project and sending us a pull request once you're done adding your changes. We will review and merge all pull requests as fast as possible and be happy to include your name on the list of authors of this document.

So far, the following people have contributed to this open-source book:

• Kayce Basques - Kayce wrote most of the original content for this book.
• Andreas Dewes - Andreas compiled the list of patterns and did most of the editing.
• Christoph Neumann - Christoph contributed material and did a large part of the editing.
• Florian Lehmann - Florian designed the modified RTD theme used for this book.

If you have contributed to this book but your name is missing from the list, feel free to add it on Github. We apologize for any omissions.

Here's the full index of all anti-patterns in this book.

.. toctree::
    :glob:
    :maxdepth: 2

    maintainability/index
    readability/index
    security/index
    performance/index
    correctness/index