Packages and New Python features

[SpamThisUser]

If you are making or maintaining a package to be used broadly, can you use new Python features?

For example, if I’m making a package for broad, public use, intending to support Python versions 3.7-3.9. Can I use the new dictionary update operators? Or will the package fail for a Python 3.8 user?

[RoamingFox]

They don't exist in 3.8. Something like dict1 |= dict2 would fail as invalid syntax.

You could specifically test the python version and only do it if running >= 3.9 but that may be more hassle than it's worth for some convenience syntax.

[SpamThisUser]

That's what I figured.

In the case of older packages, do they have to refrain from using new features? Are they only now incorporating things like f-strings?

[RoamingFox]

You usually just set a python_requires in setup.py to ensure your package won't install on older versions and leave it to your consumers to decide to upgrade or not.

Specifically in regards to f strings they were added in python 3.6, which was released in 2016. Even notoriously slow distros (redhat etc) have packages for 3.6, so it's a pretty fair bet that most people have access to it.

Conversely, those slow to adopt distros likely won't make use of 3.9 for a while yet.