Managing Multiple Python Installations on Windows

Introduction

Managing multiple Python installations on Windows can be a challenging task. With the help of pyenv, it becomes much easier and efficient. In this article, we will explore how to set up and use pyenv to effectively manage multiple Python versions on your Windows system.

Why have multiple Python installations?

Here is a non-exhaustive list of reasons why you might want to have multiple Python installations on your system:

• Open-source contributions: Contributing to open-source projects often requires running specific Python versions that the project supports. By having multiple Python installations, you can easily switch to the required version for contribution purposes.

• Legacy projects: Legacy projects may rely on older versions of Python that are no longer actively supported. If you need to maintain or work on such projects, having multiple Python installations enables you to keep the necessary older versions while using newer versions for other projects.

• Testing and development: As a developer, you may need to test your code on different Python versions to ensure its compatibility across various environments. Having multiple Python installations allows you to test your code on different versions without affecting your main development environment. If you are seriously considering testing your code on different Python versions, you should consider using tox, which aims to automate testing in various Python versions.

Overall, having multiple Python installations provides flexibility and the ability to work on a variety of projects with different requirements. Pyenv enables developers (like you) to efficiently manage various Python versions in a easy to use cli.

What is pyenv?

Pyenv is a tool that allows you to manage multiple Python versions concurrently and isolate them from the system Python ¹. It provides a straightforward and flexible way to switch between different Python versions.

Installing pyenv

A quick search on ‘pyenv’ will lead you to https://github.com/pyenv/pyenv. However, upon going through the README, you will find that pyenv is not supported on Windows. Here are some relevant excerpts from the README:

Fortunately, @kirankotari’s pyenv-win fork makes pyenv available for Windows.

Refer to the installation section for guidance on installing pyenv-win. I recommended using Chocolatey. If Chocolatey is not already installed on your system, follow the instructions here to install it.

Verifying installation

Once you have installed pyenv-win, you can verify the installation by running the following PowerShell command:

pyenv --version

If the installation is successful, you will see the version of pyenv-win installed on your system. For example:

pyenv 3.1.1

You can further confirm that pyenv-win is working correctly by running the pyenv command. This will display a list of all available commands:

pyenv

For example, you might see the following output:

pyenv 3.1.1

Usage: pyenv <command> [<args>]

Some useful pyenv commands are:
   commands     List all available pyenv commands
   duplicate    Creates a duplicate python environment
   local        Set or show the local application-specific Python version
   global       Set or show the global Python version
   shell        Set or show the shell-specific Python version
   install      Install a Python version using python-build
   uninstall    Uninstall a specific Python version
   update       Update the cached version DB
   rehash       Rehash pyenv shims (run this after installing executables)
   vname        Show the current Python version
   version      Show the current Python version and its origin
   version-name Show the current Python version
   versions     List all Python versions available to pyenv
   exec         Runs an executable by first preparing PATH so that the selected Python
   which        Display the full path to an executable
   whence       List all Python versions that contain the given executable

See `pyenv help <command>' for information on a specific command.
For full documentation, see: https://github.com/pyenv-win/pyenv-win#readme

Installing Python

To see the list of Python versions available for installation, you can run the following command:

pyenv install -l

This command displays all the available Python versions. For example, you might see the following output (truncated for brevity):

:: [Info] ::  Mirror: https://www.python.org/ftp/python
3.9.0a1-win32
3.9.0a1
3.9.0a2-win32
3.9.0a2
3.9.0a3-win32
3.9.0a3
...
3.9.10-win32
3.9.10
3.9.11-win32
3.9.11
3.9.12-win32
3.9.12
3.9.13-win32
3.9.13

To install a specific Python version, such as 3.9.10, you can use the following command:

pyenv install 3.9.10

This will initiate the download and installation process, producing output similar to:

:: [Info] ::  Mirror: https://www.python.org/ftp/python
:: [Downloading] ::  3.9.10 ...
:: [Downloading] ::  From https://www.python.org/ftp/python/3.9.10/python-3.9.10-amd64.exe
:: [Downloading] ::  To   C:\Users\<username>\.pyenv\pyenv-win\install_cache\python-3.9.10-amd64.exe
:: [Installing] ::  3.9.10 ...
:: [Info] :: completed! 3.9.10

Setting a Global Python Version

Step 1: Understanding the Global Python Version

In pyenv, the global Python version is the default version used system-wide unless overridden by a local version.

Key Points:

• The global version serves as a fallback if no other version is specified.
• A project-specific version (set with pyenv local) will take precedence only within the project’s directory.

This hierarchy allows flexibility while maintaining a fallback/default when no other version is specified.

Step 2: Viewing or Setting the Global Python Version

You can use the pyenv global command to set or view the global Python version for your system.

Example: Setting a Global Python Version

To set Python 3.9.10 as the default version, run:

pyenv global 3.9.10

Once set, Python 3.9.10 will be the default version used unless a local version is defined.