Managing Python Versions with pyenv

In the past, when using Python, I mostly relied on Conda for management. Nowadays, pyenv has become the go-to tool.

In this article, I briefly document how to install and use pyenv and provide necessary supplemental information for different operating systems.

Prerequisites​

Before installing pyenv, you need to have Git installed on your system.

Common Issues and Solutions​

Here are a few important cases and their solutions:

• Missing dependencies Please first install all necessary packages and build tools according to the official pyenv dependency guide.

• zlib extension compilation failure

  The common error message is:

  • ERROR: The Python zlib extension was not compiled. Missing the zlib?

  Solution:

  • On Ubuntu/Debian systems, install zlib1g and zlib1g-dev:

    sudo apt install zlib1g zlib1g-dev
    
  • On macOS, if you installed zlib with Homebrew, set the environment variable:

    CPPFLAGS="-I$(brew --prefix zlib)/include" pyenv install -v <python-version>
    

• OpenSSL extension compilation failure

  If you see:

  • ERROR: The Python ssl extension was not compiled. Missing the OpenSSL lib?

  Solution:

  • Make sure the OpenSSL development packages are installed (e.g., on Ubuntu use sudo apt install libssl-dev, on Fedora use sudo dnf install openssl-devel).
  • If OpenSSL is installed in a non-standard location, set the following:

    CPPFLAGS="-I<openssl-install-path>/include" \
    LDFLAGS="-L<openssl-install-path>/lib" \
    pyenv install -v <python-version>
    

• System resources are insufficient

  If you encounter the "resource temporarily unavailable" error, try reducing the make parallelism:

  MAKE_OPTS='-j 1' pyenv install <python-version>
  

• python-build definition not found

  If you encounter the python-build: definition not found error, update the python-build definitions:

  cd ~/.pyenv/plugins/python-build && git pull
  

• macOS architecture-related errors

  If you see errors like ld: symbol(s) not found for architecture x86_64 or ld: symbol(s) not found for architecture arm64, ensure that the Homebrew packages match the correct architecture and check if additional environment variables (such as CPPFLAGS, LDFLAGS, and CONFIGURE_OPTS) need to be set.

For more detailed information, refer to Common build problems.

Cross-platform Considerations​

• Linux/macOS:

  • The installation method is generally the same, and you can directly use the commands in the next section.
  • Install the necessary compilation dependencies based on your operating system (e.g., on Ubuntu, you may need to install build-essential, libssl-dev, zlib1g-dev, etc.).

• Windows users:

  • pyenv is natively designed for Unix-like environments, so it’s recommended to use the pyenv-win version.
  • Alternatively, you can use WSL, Git Bash, or similar tools on Windows to get a Unix-like environment.

• Other Shell Users:

  • If you use a shell other than bash or zsh (such as fish), refer to the corresponding shell configuration files for adjustments.

Installing pyenv​

1. Run the installation command:

   You can quickly install pyenv with the following command:

   curl https://pyenv.run | bash
   

   This command will fetch and execute the installation script from the pyenv-installer repository on GitHub.

2. Configure your shell environment:

   After installation, follow the setup guide to configure your shell environment to ensure pyenv works properly.

   For bash, add the following lines to your .bashrc file:

   export PATH="$HOME/.pyenv/bin:$PATH"
   eval "$(pyenv init --path)"
   eval "$(pyenv virtualenv-init -)"
   

   For zsh, add the same lines to your .zshrc file; for other shells, refer to their respective configuration files.

3. Restart your shell:

   After completing the above steps, reload the configuration:

   exec $SHELL
   

Using pyenv​

Once installed and configured, you can use pyenv to manage multiple Python versions:

• Install a new Python version:

  pyenv install 3.10.14
  

• Switch the global Python version:

  pyenv global 3.10.14
  

• Use a specific version in a particular directory:

  pyenv local 3.8.5
  

Virtual Environments​

Virtual environments are crucial in Python development as they help you use independent Python versions and dependencies in different projects, avoiding conflicts.

Installation​

pyenv provides the pyenv-virtualenv plugin, making virtual environment management more convenient.

This functionality is now integrated into pyenv and can be used directly:

pyenv virtualenv 3.10.14 your-env-name

Here, 3.10.14 is the Python version you want to use (make sure it's installed), and your-env-name is the name of the virtual environment.

Usage​

Activate the virtual environment:

pyenv activate your-env-name

Deleting​

When you no longer need the virtual environment, you can delete it with:

pyenv virtualenv-delete your-env-name

Updating pyenv​

If you need to update pyenv to the latest version, you can follow these methods:

• Using the update plugin: If you’ve installed the pyenv-update plugin, you can directly execute:

  pyenv update
  

• Manual update: Go to the ~/.pyenv directory and update using Git:

  cd ~/.pyenv
  git pull
  

Removing pyenv​

If you decide to stop using pyenv, follow these steps to remove it:

1. Remove the pyenv installation directory:

   rm -fr ~/.pyenv
   

2. Clean up shell configurations:

   Remove or comment out the lines related to pyenv in .bashrc, .zshrc (or other shell configuration files), then restart the shell:

   exec $SHELL
   

Conclusion​

These are the commonly used commands. I hope you have a great Python environment!