Correct usage of different Python versions

Is there a rule of thumb of how to use Python versions?

I have downloaded and installed Python v3.10.4 being it the latest release. Would it be fully backward-compatible with all the previous versions down to Python v3.7.4?

Or do I have to install every single release of Python v3.x and then match a corresponding version to a corresponding code to stay on the safe side?

I am a medior C/C++ programmer who is new to Python.

Newer python versions comes with newer syntax to do stuffs that previously required more code lines. If you stay with the syntax that are supported in v3.7 you could assume that it will work with v3.10 but vice verca might not be true and for you to be able to use those newer syntax, you will require latest versions.

Hope that helps.

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It’s true that most Python code that runs on 3.7 also runs on 3.10, so you could just install the latest version and might be fine.
But it’s not 100%. You could check for backward incompatible changes and deprecated or removed features of 3.10 here:

If you need to support multiple versions it’s not uncommon to install each version e.g. 3.7, 3.8, 3.9, and 3.10. On Windows you automatically get the py.exe launcher installed, so you can run py -3.8 etc. to select the different versions.

The answer to your question depends on what you are trying to do.

Why do you you think you need to “install every single release of Python v3.x”? What do you gain from it?

“Stay on the safe side” of what?

If your aim is to write a public library that supports versions 3.7 onwards, then of course you need to test that library under at least one patch for each minor version: at least one version each of 3.7.x, 3.8.x, 3.9.x and 3.10.x.

If your aim is to write scripts for your own use, then the existence of older versions is irrelevant. Just pick a version and use it.

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Depending on your comfort level and available resources, you may
find it’s sufficient to test with the oldest and newer minor
versions of Python you intend to support (so, for example, latest
3.7.x and 3.10.x). It’s usually (but not always) safe to assume that
code which works on two minor versions of the same major version
will work on the minor versions between them, particularly if you
don’t have any code which branches logic based on interpreter
version matches.