Need multiple Python versions without fighting apt? pyenv is the cleanest way.
Below is the 5-minute setup I use on Pop!_OS 22.04 (LTS) — it works the same on vanilla Ubuntu 22.04.

1 · Prereqs – dev libraries & build tools

pyenv compiles CPython from source, so we have to give its build script every *-dev dependency it needs.

sudo apt update
sudo apt install -y \
  make build-essential            \
  libssl-dev zlib1g-dev           \
  libbz2-dev libreadline-dev      \
  libsqlite3-dev libncursesw5-dev \
  liblzma-dev tk-dev              \
  curl git                         # helpers

(If you already did this, you’re golden.)

2 · Install pyenv

# 1) Clone pyenv into ~/.pyenv
curl https://pyenv.run | bash

# 2) Add it to your shell
echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc
echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc
echo -e 'eval "$(pyenv init --path)"\n' >> ~/.bashrc
exec $SHELL          # reload the shell

Zsh? Drop the lines into ~/.zshrc.

3 · Build the Pythons you need

# Latest patch releases as of June 2025
pyenv install 3.12.11   # newest stable
pyenv install 3.11.9    # LTS-ish for many libs

Grab a coffee — the first build can take a few minutes.

4 · Make Python 3.12 your global default

pyenv global 3.12.11
python --version        # → Python 3.12.11

Switch projects on-the-fly:

pyenv local 3.11.9      # writes .python-version in the folder

5 · Bonus: keep everything tidy

• Uninstall a version: pyenv uninstall 3.11.9
• List what’s installed: pyenv versions
• Update pyenv itself: git -C "$(pyenv root)" pull

That’s it!

You now have a sandboxed Python 3.12 interpreter (with SSL, readline, curses, etc.) plus 3.11 for legacy projects — all without touching the system Python that apt depends on. Happy hacking!