Joel Spolsky’s infamous Joel Test is a quick heuristic test for checking a software engineering team’s technical chops. I’ve come up with a similar test that we can use to decide whether a new package we’re considering depending on is well-maintained.
The preface of Software Engineering at Google opens with this thesis:
The descriptor protocol allow us to completely customize attribute access. Python’s documentation describes the protocol with types involved described with words. Let’s look at how we can write those as type hints.
Earlier this week I shared my Python script template. Here’s an extended version with sub-command support, and an example script.
When dealing with evolvng APIs, it may be useful to rename an attribute in a class, but keep the old name around for backwards compatibility. This would mean making one attribute an alias for another. In this post we’ll look at two ways to achieve this.
functools.partial() in DjangoI remain convinced that Python’s functools.partial() is underappreciated. Following my previous post, here are three more ways to use partial() with Django.
It’s fundamentally useful to exit your program when it’s done. Here are five(!) ways to do so in Python.
Python is great for writing scripts for the command line. In this post we’ll look at my script template, an example script, and some alternative versions (without type hints, and in async flavour).
print()If you’re embarrassed at debugging with print(), please don’t be - it’s perfectly fine! Many bugs are easily tackled with just a few checks in the right places. As much as I love using a debugger, I often reach for a print() statement first.
Django 4.0 had its first alpha release last week and the final release should be out in December. It contains an abundance of new features, which you can check out in the release notes. In this post we’ll look at the changes to testing in a bit more depth.
I recently converted this blog to Pelican, a Python powered static site generator. On the way I added a few customizations. One customization is a Jinja template filter to truncate a post’s HTML as a summary, using Python’s HTMLParser class. Here’s how I wrote it.
Sometimes pip install will flag a warning saying “The candidate selected for download or install is a yanked version”. For example, if we install attrs version 21.1.0:
Many languages follow the syntax of C, and use semicolons to indicate the end of a statement. For example, in JavaScript:
Take this function:
Django deprecates a small list of features with every feature release, requiring us to update our projects, which can be monotonous. Today I’m announcing a new tool I’ve created, django-upgrade, that automates some of this drudgery for us all.
When Lambda@Edge first came out, I added it to my blog’s CloudFront distribution in order to add security headers. Then, when Lambda@Edge added Python support, I converted my function from JavaScript to Python.
Black is the de facto standard code formatter for Python, and these days I use it on all my projects. blacken-docs is a tool that also allows you to apply Black to code samples in your docs. I recently rolled it out on my projects to great effect.
I started this blog in 2014 using the popular Jekyll. Whilst it served me well, I’ve wanted to migrate to a Python-based tool for a while now, for a few reasons:
types moduleWriting type hints gives us some familiarity with the typing module. But Python also includes the similarly-named types module, which can also come in handy. Let’s look at the history of these two modules, some use cases of types, and one way in which it’s not so useful.
Python’s re module lets us search both str and bytes strings with regular expressions (regexes). Our type checker can ensure we call re functions with the correct types, thanks to some parametrized classes.
Here’s a recipe that combines typing.Literal with @overload to define a function that switches its return type based on the value of an argument.
“The Boolean Trap” is a programming anti-pattern where a boolean argument switches behaviour, leading to confusion. In this post we’ll look at the trap in more detail, and several ways to avoid it in Python, with added safety from type hints.
typing.LiteralTo put it tautologically, type hints normally specify the types of variables. But when a variable can only contain a limited set of literal values, we can use typing.Literal for its type. This allows the type checker to make extra inferences, giving our code an increased level of safety.
I released my book “Speed Up Your Django Tests” over a year ago, in May 2020. Since then, we’ve seen two major Django releases, including a whole bunch of test-related changes, some of which I worked on as part of the book.
typing.cast()Python’s dynamism means that, although support continues to expand, type hints will never cover every situation. For edge cases we need to use an “escape hatch” to override the type checker.