Adam Hill posted a question on Mastodon: he wants a model field that uses choices that doesn’t generate a database migration when the choices change. This post presents my answer. First, we’ll recap Django’s default behaviour with choice fields, a solution with callable choices, and the drawbacks.
In Python, a mixin class is a class that is not intended to be used directly, but instead “mixed in” to other classes through multiple inheritance. Mixins are not really a language feature but more of a conventional pattern allowed by Python’s multiple inheritance rules. Unfortunately, adding type hints to mixin classes can be tricky because they implicitly require subclasses to fit a certain shape.
GitHub-Flavored Markdown (GFM) is GitHub’s variant of Markdown, with extra features like task lists and alert boxes. It’s used in issues, pull requests, comments, and many other places on GitHub.
Django 5.2 was released last Wednesday, another exciting step forward for our favourite web framework. It comes with a composite of new features, contributed to by many, some of which I am happy to have helped with. Below is my pick of highlights from the release notes.
Do you see this message when you open a new terminal session?
Last week, I released the second update to my book Boost Your Git DX. Today I’m happy to announce that I have released a free sample of the book.
Today I have released the second update to Boost Your Git DX, my book of developer experience (DX) recommendations for using Git. Since the last update (2024-04-04), it has grown again by 28 pages, for a new total of 391 pages!
hyperfine is a neat tool for benchmarking commands. If you provide it multiple commands, its output includes a comparison, saying which is the fastest, and by how much.
Some Python packages require native libraries to be installed on your system when you install them. For example, mysqlclient requires libssl and libcrypto. If those libraries are missing at install time, clang, the C compiler, fails with a message like:
JavaScript’s import statement lets module scripts import objects from other scripts. For example, you can define a script as a module in HTML:
Browser extensions can run JavaScript within the content of your tabs. This means they can trigger messages that appear in the devtools console. For example, one extension I use logs this warning on every tab:
You might see this message when running pytest on your Django project:
unittest.mockA few days ago, I blogged about debugging unraisable exceptions with Rich. Here’s a sequel on testing that some block of code doesn’t trigger any unraisable exceptions.
color.ui or --colorBy default, Git only colourizes in its output when writing to an interactive terminal. Sometimes, this heuristic isn’t accurate, for example, when you’re piping Git output through another command. In such cases, you can force colourization on or off with either the color.ui configuration option or the --color option. Let’s look at both in turn.
Take this Python class:
Okay, so you just ran git pull on a branch, and something broke, so you want to undo it. Here are two ways how.
sys.monitoringPython 3.12 introduced sys.monitoring, a new framework for “monitoring” tools like debuggers and profilers to hook into. It provides fine-grained control so tools can listen only to certain events on specific lines of code. The framework came from PEP 669, thanks to Mark Shannon of the Faster CPython team.
Sometimes, tests need temporary files or directories. You can do this in Python’s unittest with the standard library tempfile module. Let’s look at some recipes to do so within individual tests and setUp().
{% url '' %}Previously, I covered using 1/0 to crash Python within minimal typing, useful to quickly answer questions like “does the code even get here?”. Recently, I wanted to do the same in Django templates, to trace if a given template was even being rendered, and under which code paths.
Yesterday, I held another quiz at the December edition of Django London. The quiz is a regular tradition at our meetup, a way of having a more relaxed event in December and giving away some nice prizes. This was the sixth quiz that I’ve presented, and the seventh overall.
Here’s another technique for using pdb within Django. I will add this to the new debugging chapter of Boost Your Django DX in a future update.
{% breakpoint %} tagIn my recent Boost Your Django DX update, I added a new chapter on debuggers. Here’s an extra technique I didn’t finish in time for the update, but I will include it in the next one.
breakpoint()Python’s breakpoint() function opens its debugger, pdb, which pauses the program and allows you to inspect and modify things. Let’s look at an example of using it within a Django view, from a sample project included in Boost Your Django DX.
Heavy refactoring of models can leave a Django project with “ghost tables”, which were created for a model that was removed without any trace in the migration history. Thankfully, by using some Django internals, you can find such tables.
rev-listgit rev-list lists details about commits (also known as “revisions”, hence the name). Its --count option outputs the count of commits in the given range. Pass it @, the short alias for HEAD, to count commits on the current branch: