Why Upgrade to Python 3?
Forget the sort annotations, asynchronous mills & comprehensions, and plenty of different cool options — the one most essential cause for upgrading is that Python 2 is approaching its End of Life in 2020. Even Instagram is making the change. With nearly all of Python’s hottest packages supporting each variations, there’s by no means been a greater time to take the leap.
Currently, most of our microservices are written in Python 3 from the bottom up. There are a couple of older companies nonetheless working Python 2 that we’re within the means of upgrading or relocating. For instance, we’ve eliminated a lot of the performance from our oldest legacy venture, with a aim of eradicating it altogether.
Keeping Forward Compatibility in Mind
Unless your codebase is small and your unit take a look at protection is close to excellent, you’ll wish to preserve ahead compatibility in thoughts. Fortunately, it’s doable to proceed growing new options whilst you tweak your codebase to arrange for migration.
Here’s our technique and a few instruments that can assist you do exactly that:
Start With the Latest Python 2
We discovered that an incredible place to begin is to replace to the most recent model of Python 2 (v2.7.13 as of this writing). This revealed some points with our dependencies that we needed to resolve by upgrading to newer variations. Depending on which model you’re utilizing, chances are you’ll discover essential safety updates within the patch variations similar to TLS 1.1 & 1.2 help, in v2.7.9, for instance. Updating TLS is essential for net primarily based functions, as TLS 1.0 has been on its method out since 2015. This means there’s a huge push for organizations to maneuver previous merely deprecating TLS 1.0, and disabling it outright.
Tests, Tests, and More Tests
In my final weblog submit, I mentioned the significance of writing unit checks. It’s notably essential in non-compiled languages like Python the place a easy syntax error will trigger a runtime crash. Maintaining a full take a look at suite with appropriate code protection is a big boon to catching version-specific points. Set up a Python 3 setting along with your library or service and run your take a look at suite — you’re more likely to discover one thing improper.
The Road to Python 3 is Paved with Small Boulders
Thankfully, there aren’t many main highway blocks when making the change within the language itself. There are, nonetheless, many hindrances that had been launched for good technical causes. These obstacles are sometimes greppable and simple to seek out.
For instance, you won’t care that the string kind was modified from a byte array right into a unicode character array, however your code would possibly. The six library will help — it supplies aliases text_type and binary_type which map, model agnostically, to their respective elements in every model. So, you may exchange current references with one which can be accepted throughout each variations.
Similarly, in Python 3, metaclass declaration syntax modified from being a category variable to part of the category signature. Six supplies a wrapper known as with_metaclass, which matches into the signature however nonetheless works in Python 2, because of a bunch of Python magic. The library additionally supplies quite a lot of different helpful lessons and strategies.
Other Useful Tools
Linters are superior — you may set them as much as run on automated builds both earlier than or after your unit checks. Here are some helpful instruments that determine migration issues, the primary two of which we use right here at Pixability:
PyLint: Has a parameter for linting Python 3-specific compatibility points.
caniusepython3: Claims to have stricter linting than PyLint, additionally checks for compatibility.
2to3: Converts Python 2 to Python 3 code. Probably extra helpful for small codebases, however comes packaged alongside the Python interpreter.
Don’t Get Left Behind
There are essential safety patches and efficiency enhancements to be gained from upgrading patch variations alone. Python 2 is nearing its finish of life, and also you don’t wish to be caught attempting to improve on the final second. Fortunately, there are a lot of instruments obtainable that can assist you alongside the best way.
“Now, be courageous, and don’t look again.” – Shmi Skywalker
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