pyenv is awesome and has changed the way that I manage my Python environments. One tiny annoyance is that it takes a looong time to install each Python version, which of course makes sense, since it has to download and compile each version on your machine. But it’s not a big deal, since you generally just do this once and then not again until you really need to upgrade to a different Python version.

Recently, though, I was working on a project that uses tox to make sure that the project runs on multiple Python versions, in this case 3.6, 3.7, 3.8, 3.9. The specific versions were included in the .python-version file, which looked like this:

3.9.0
3.8.6
3.7.9
3.6.12

I didn’t have all of these installed, so rather than doing pyenv install 3.9.0 and then waiting a few minutes, and then repeating the process for each version, I wrote up this little script, which I named pyinstall.sh:

#!/bin/bash
# Install all versions specified in .python-version
set -ex

while read version; do
    pyenv install -s "$version"
done <.python-version

Since pyenv is nice enough to include the -s flag which means “skip if already installed”, this can be run as many times as you want and it will only install the version if it’s not already installed