Features get added. So you can't use a match statement in 3.9 but you can in 3.10. If you write a library you need to be conservative in which features you use

Features get added. So you can't use a match statement in 3.9 but you can in 3.10. If you write a library you need to be conservative in which features you use or applications can't use you. Why not just upgrade applications ASAP? Sometimes things are removed over three or so versions. So you can't move from e.g. 3.9 to 3.10 without making sure you're importing types from the correct location: https://docs.python.org/release/3.9.0/whatsnew/3.9.html https://docs.python.org/release/3.9.0/whatsnew/3.9.html > Aliases to Abstract Base Classes in the collections module, like collections.Mapping alias to collections.abc.Mapping, are kept for one last release for backward compatibility. They will be removed from Python 3.10. These things are planned. It's just much much harder to handle this because you need the interpreter at runtime while in compiled languages you just use `-std=C99` and you can compile the code and then link.