How many Python versions do I need?

[kenatsun]

I'm about to upgrade a Window machine from Win 7 to Win 10, with a clean install. So I will have to reinstall all my apps, including Python.

Currently, under Win 7, I see that three versions are installed: Python 2.6.6, 2.7.8, and 3.4.2. I'm not quite sure why so many versions. I didn't install all of them. I'm guessing that some other Python app auto-installed some of them, but I don't know.

My question is: If after doing the clean install of Win 10, if I just install the latest version of Python, will all the Python apps on my machine still run? Or will I have to install all three existing versions?

~ Thanks in advance
~ Ken

[ichabod801]

It depends on the Python apps on your machine. If they were written for 2.x, they may not run in the latest 3.x version. Version 3.0 broke backward compatibility. However, as of three days ago no version before 3.0 is supported. So I would recommend installing the latest version, and then if any of your applications don't run, look for updated versions of those applications that do run in 3.x.

[kenatsun]

Thanks; I'll try that.

Is it true that an app written for a given dot-release (e.g. 3.4.2) should still work under the latest release in that same series (e.g. the latest release of 3.x)?

Also, even though 2.x support is discontinued, is it still possible to download and install the last version of 2.x, if necessary?

[ichabod801]

Is it true that an app written for a given dot-release (e.g. 3.4.2) should still work under the latest release in that same series (e.g. the latest release of 3.x)?

Yes. Code from 3.0 up should run in the latest release (3.8.1). Of course, code written in 3.8.1 might not run in 3.4.2.

Also, even though 2.x support is discontinued, is it still possible to download and install the last version of 2.x, if necessary?

Yes. Older releases are available here.