Let’s start with Python

We're finally here!

But first, let us tell you what Python is. Python is a very popular programming language that can be used for creating websites, games, scientific software, graphics, and much, much more.

Python originated in the late 1980s and its main goal is to be readable by human beings (not only machines!). This is why it looks simpler than other programming languages, but don't worry – Python is also really powerful!

Python installation

If you already worked through the installation steps, there's no need to do this again – you can skip straight ahead to the next chapter!

First check to see if you already have pyenv installed by running this in a terminal window:

pyenv

If it is already installed, either update it using pyenv update or using the package manager that you used to install it.

If it is not installed you can install it using the following command, pasted into a new terminal window:

curl https://pyenv.run | bash

The output of the command tells you to add certain lines to your startup files for your terminal sessions. Follow the PyEnv setup instructions copied below - if you are unsure which section to follow, you are probably using a bash shell.

• For bash:

  Stock Bash startup files vary widely between distributions in which of them source which, under what circumstances, in what order and what additional configuration they perform. As such, the most reliable way to get Pyenv in all environments is to append Pyenv configuration commands to both .bashrc (for interactive shells) and the profile file that Bash would use (for login shells).

  First, add the commands to ~/.bashrc:

  echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc
  echo 'command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc
  echo 'eval "$(pyenv init -)"' >> ~/.bashrc
  echo 'eval "$(pyenv virtualenv-init -)"' >> ~/.bashrc
  

  Then, if you have ~/.profile, ~/.bash_profile or ~/.bash_login, add the commands there as well. If you have none of these, add them to ~/.profile.

  • to add to ~/.profile:

    echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.profile
    echo 'command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.profile
    echo 'eval "$(pyenv init -)"' >> ~/.profile
    echo 'eval "$(pyenv virtualenv-init -)"' >> ~/.profile
    

  • to add to ~/.bash_profile:

    echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bash_profile
    echo 'command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bash_profile
    echo 'eval "$(pyenv init -)"' >> ~/.bash_profile
    echo 'eval "$(pyenv virtualenv-init -)"' >> ~/.bash_profile
    

• For Zsh:

  echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.zshrc
  echo 'command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.zshrc
  echo 'eval "$(pyenv init -)"' >> ~/.zshrc
  echo 'eval "$(pyenv virtualenv-init -)"' >> ~/.zshrc
  

  If you wish to get Pyenv in noninteractive login shells as well, also add the commands to ~/.zprofile or ~/.zlogin.

• For Fish shell:

  Execute this interactively:

  set -Ux PYENV_ROOT $HOME/.pyenv
  set -U fish_user_paths $PYENV_ROOT/bin $fish_user_paths
  

  And add this to ~/.config/fish/config.fish:

  pyenv init - | source
  

  Bash warning: There are some systems where the BASH_ENV variable is configured to point to .bashrc. On such systems, you should almost certainly put the eval "$(pyenv init -)" line into .bash_profile, and not into .bashrc. Otherwise, you may observe strange behaviour, such as pyenv getting into an infinite loop. See #264 for details.

  Proxy note: If you use a proxy, export http_proxy and https_proxy, too.

Restart your shell

for the PATH changes to take effect.

  exec "$SHELL"

Install Python build dependencies

Install Python build dependencies before attempting to install a new Python version.

You can now begin using Pyenv.

Installing a Python Version with PyEnv

Use the pyenv command in your terminal to install a recent version of Python:

pyenv install 3.9.13

The PyEnv installation wiki provides a list of common issues when installing Python versions on different operating systems.

You can now activate this version of Python just for this shell session:

pyenv shell 3.9.13

Now if you check the Python version it should be 3.9.13:

python --version

See the PyEnv documentation for more detailed usage of the pyenv command.