pyenv

List all available commands

$ pyenv commands

$ pyenv versions

$ pyenv install --list

$ pyenv install [2.7.10]

$ pyenv uninstall [2.7.10]

$ pyenv global [2.7.10]

$ pyenv local [2.7.10]

pyenv []

commands
    List all available pyenv commands.

local
    Set or show the local application-specific Python version. If no version is specified, the local version is removed.

global
    Set or show the global Python version. If no version is specified, the global version is displayed.

shell
    Set or show the shell-specific Python version. If no version is specified, the shell version is displayed.

install
    Install a Python version. 'pyenv install --list' displays all available versions.

uninstall
    Uninstall a specific Python version.

versions
    List all Python versions available to pyenv.

version
    Display the currently active Python version and its origin.

version-name
    Display the currently active Python version name.

version-file
    Display the file from which the current Python version is read.

which
    Display the full path to an executable.

rehash
    Rehash pyenv shims (refresh the list of available commands).

doctor
    Diagnose common problems with pyenv setup.

prefix
    Display pyenv's prefix for a specific Python version.

pyenv lets you easily switch between multiple Python versions. It's a simple, unobtrusive, and follows the UNIX tradition of single-purpose tools that do one thing well. It doesn't require modifying your PATH permanently until you initialize it and works by intercepting Python commands using shim executables inserted into your PATH. When you execute a Python command, pyenv determines which Python version to use based on your project, environment variables, and global settings. This allows you to work on different projects requiring different Python versions without interference.

Key features include: Installing multiple Python versions, easy switching between versions, isolated environments for different projects, and integration with virtualenv and other tools. pyenv aims to be a lightweight and flexible solution, avoiding conflicts with system Python installations and other development tools.

It is important to rehash pyenv after installing new versions of Python or installing packages with executable scripts. Using virtualenv with pyenv is a common pattern and highly recommended for project isolation.

For pyenv to work properly, it needs to be initialized in your shell environment. This typically involves adding a few lines to your .bashrc, .zshrc, or equivalent configuration file. These lines ensure that pyenv's shims are added to your PATH and that the pyenv environment is properly loaded. Check the pyenv documentation for specific instructions for your shell.

pyenv uses 'shims' to intercept calls to Python executables. These shims are lightweight scripts placed in the $(pyenv root)/shims directory. When you run a command like python, the shim is executed first. The shim then determines the appropriate Python version to use and forwards the command to the correct Python executable.

pyenv emerged as a response to the challenges of managing multiple Python versions in development environments. Prior to pyenv, developers often relied on system-level installations or manual manipulation of environment variables, leading to conflicts and inconsistencies. pyenv's development focused on providing a lightweight, user-friendly, and non-intrusive solution for version management. It gained popularity as it simplified workflows, reduced conflicts, and allowed developers to easily switch between different Python versions depending on project requirements. The continuous development incorporates bug fixes, feature enhancements, and improvements to compatibility with various Python versions and package management tools.

virtualenv(1), python(1)