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I used python installer (downloaded from www.python.org) to install python3.8 & python 3.9. Is it possbile to switch them between different projects ? I don't think pyenv will work here (yet) because pyenv can only switch the versions installed by it. https://github.com/pyenv/pyenv/issues/1628 confirms this.

So for example, when run pyenv versions on my machine

➤ pyenv versions
* system (set by /Users/qiulang/.pyenv/version)
  3.4.0
  3.5.3
  3.6.10

The system version there is python3.9.

Most of my python scripts need 3.8 because I used pip3 install the packages under 3.8.

I installed 3.9 to experience the latest feature but I don't won't 3.9 to be my default python3, otherwise I need to installed the packages all over again.

Now I can't find a way to do that so I had to change my script from

#! /usr/bin/env python3 to #! /usr/local/bin/python3.8 as a temporary solution.

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I had the same question just a week or so ago. There's an extension for pyenv called pyenv-register. I installed that and used it to register each of my Homebrew installed Python versions. This gives you a pyenv version for each Python you register that looks something like system-3.9.0.

After registering the Homebrew installed Python versions, I created symlinks in ~/.pyenv/versions to create some simpler aliases for each of the versions I registered. Here's what that directory looks like on my system:

lrwxr-xr-x  1 steve  staff    6 Jun 23  2019 2 -> 2.7.16
lrwxr-xr-x  1 steve  staff    6 Jun 23  2019 2.7 -> 2.7.16
drwxr-xr-x  6 steve  staff  192 Jun 23  2019 2.7.16
lrwxr-xr-x  1 steve  staff    5 Jun 23  2019 3 -> 3.7.3
lrwxr-xr-x  1 steve  staff    5 Jun 23  2019 3.7 -> 3.7.3
drwxr-xr-x  6 steve  staff  192 Jun 23  2019 3.7.3
lrwxr-xr-x  1 steve  staff    5 Nov 14 14:51 3.8 -> 3.8.6
lrwxr-xr-x  1 steve  staff   12 Nov 14 14:51 3.8.6 -> system-3.8.6
lrwxr-xr-x  1 steve  staff    5 Nov 14 14:51 3.9 -> 3.9.0
lrwxr-xr-x  1 steve  staff   12 Nov 14 14:51 3.9.0 -> system-3.9.0
drwxr-xr-x  6 steve  staff  192 Nov 14 14:48 system-3.8.6
drwxr-xr-x  6 steve  staff  192 Nov 14 14:50 system-3.9.0

and here's what pyenv versions gives me:

% pyenv versions
  system
  2
  2.7
  2.7.16
* 3 (set by /Users/steve/.pyenv/version)
  3.7
  3.7.3
  3.8
  3.8.6
  3.9
  3.9.0
  system-3.8.6
  system-3.9.0

This works great for me, having installed my new Pythons with Homebrew. I assume that it will work just as well for Python versions installed with a downloaded installer. I hope this helps you out!

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3 Comments

Thanks I will try that and maybe get back to you.
I installed the plugin but when pyenv register I got the error "virtualenv is not installed to /Library/Frameworks/Python.framework/Versions/3.8/bin/python3.8 ... pyenv: Failed to download virtualenv" So pyevn register failed.
I still can't solve the problem with pyenv-register. I raise an issue to them and no reply. So I have to give it up :$

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