PYENV(1)

NAME
pyenv - Simple Python version management

SYNOPSIS
pyenv <command> [<args>]

DESCRIPTION
pyenv lets you easily switch between multiple versions of Python. It's simple, unobtrusive, and follows the UNIX tradition of single-purpose tools that do one thing well.

 To start using pyenv

1.  Append the following to $HOME/.bashrc

    if command -v pyenv 1>/dev/null 2>&1; then
       eval "$(pyenv init - bash)"
    fi

    Appending this line enables shims. Please make sure this line is placed toward the end of the shell configuration file since it manipulates PATH during the initialization.

    Debian note:
        Modify only your ~/.bashrc file instead of creating
        ~/.bash_profile

        Zsh note: Modify your ~/.zshrc file instead of ~/.bashrc

        Warning: If you configured your system so that BASH_ENV variable points to .bashrc. You should almost certainly put the above mentioned line into .bash_profile, and not into .bashrc. Otherwise you may observe strange behaviour, such as pyenv getting into an infinite loop. See #264 https://github.com/pyenv/pyenv/issues/264 for details.

2.  Restart your shell so the path changes take effect. You can now begin using pyenv.

    exec "$SHELL"

3.  Install Python versions into $(pyenv root)/versions. For example, to download and install Python 3.6.12, run:

    pyenv install 3.6.12

NOTE: If you need to pass configure option to build, please use CONFIGURE_OPTS environment variable. If you are having trouble installing a python version, please visit the wiki page about Common Build Problems https://github.com/pyenv/pyenv/wiki/Common-build-problems

Proxy note: If you use a proxy, export HTTP_PROXY and HTTPS_PROXY environment variables.

  Stop using pyenv
The simplicity of pyenv makes it easy to temporarily disable it, or uninstall from the system. To disable pyenv managing your Python versions, simply remove the pyenv init line from your shell startup configuration. This will remove pyenv shims directory from PATH, and future invocations like python will execute the system Python version, as before pyenv.

pyenv will still be accessible on the command line, but your Python apps won't be affected by version switching.

COMMAND LINE OPTIONS
Like git, the pyenv command delegates to subcommands based on its first argument.

  Some useful pyenv commands are:

commands
    List all available pyenv commands

exec
    Run an executable with the selected Python version

global
    Set or show the global Python version(s)

help
    Display help for a command

hooks
    List hook scripts for a given pyenv command

init
    Configure the shell environment for pyenv

install
    Install a Python version using python-build

local
    Set or show the local application-specific Python version(s)

prefix
    Display prefix for a Python version

rehash
    Rehash pyenv shims (run this after installing executables)

root
    Display the root directory where versions and shims are kept

shell
    Set or show the shell-specific Python version

shims
    List existing pyenv shims

uninstall
    Uninstall Python versions

version
    Show the current Python version(s) and its origin

version-file
    Detect the file that sets the current pyenv version

version-name
    Show the current Python version

version-origin
    Explain how the current Python version is set

versions
    List all Python versions available to pyenv

whence
    List all Python versions that contain the given executable

which
    Display the full path to an executable

See `pyenv help <command>' for information on a specific command. For full documentation, see COMMAND REFERENCE section

OPTIONS

-h, --help
    Show summary of options.

-v, --version
    Show version of program.

COMPARISON

pyenv does...

•   Let you change the global Python version on a per-user basis.

•   Provide support for per-project Python versions.

•   Allow you to override the Python version with an environment variable.

•   Search commands from multiple versions of Python at a time. This may be helpful to test across Python versions with tox

In contrast with pythonbrew and pythonz, pyenv does not...

•   Depend on Python itself. pyenv was made from pure shell scripts. There is no bootstrap problem of Python.

•   Need to be loaded into your shell. Instead, pyenv's shim approach works by adding a directory to your $PATH.

•   Manage virtualenv. Of course, you can create virtualenv yourself, or pyenv-virtualenv to automate the process.

How It Works
At a high level, pyenv intercepts Python commands using shim executables injected into your PATH, determines which Python version has been specified by your application, and passes your commands along to the correct Python installation.

  Understanding PATH
When you run a command like python or pip, your operating system searches through a list of directories to find an executable file with that name. This list of directories lives in an environment variable called PATH, with each directory in the list separated by a colon:

    /usr/local/bin:/usr/bin:/bin

Directories in PATH are searched from left to right, so a matching executable in a directory at the beginning of the list takes precedence over another one at the end. In this example, the /usr/local/bin directory will be searched first, then /usr/bin, then /bin.

  Understanding Shims
pyenv works by inserting a directory of shims at the front of your PATH:

    $(pyenv root)/shims:/usr/local/bin:/usr/bin:/bin

Through a process called rehashing, pyenv maintains shims in that directory to match every Python command (python,pip,etc...) across every installed version of Python

Shims are lightweight executables that simply pass your command along to pyenv. So with pyenv installed, when you run, say, pip, your operating system will do the following:

•   Search your PATH for an executable file named pip

•   Find the pyenv shim named pip at the beginning of your PATH

•   Run the shim named pip, which in turn passes the command along to pyenv

  Choosing the Python Version
When you execute a shim, pyenv determines which Python version to use by reading it from the following sources, in this order:

1.  The PYENV_VERSION environment variable (if specified). You can use the pyenv shell command to set this environment variable in your current shell session.

2.  The application-specific .python-version file in the current directory (if present). You can modify the current directory's .python-version file with the pyenv local command.

3.  The first .python-version file found (if any) by searching each parent directory, until reaching the root of your filesystem.

4.  The global $(pyenv root)/version file. You can modify this file using the pyenv global command. If the global version file is not present, pyenv assumes you want to use the "system" Python. (In other words, whatever version would run if pyenv weren't in your PATH.)

NOTE: You can activate multiple versions at the same time, including multiple versions of Python2 or Python3 simultaneously. This allows for parallel usage of Python2 and Python3, and is required with tools like tox. For example, to set your path to first use your system Python and Python3 (set to 2.7.9 and 3.4.2 in this example), but also have Python 3.3.6, 3.2, and 2.5 available on your PATH, one would first pyenv install the missing versions, then set pyenv global system 3.3.6 3.2 2.5. At this point, one should be able to find the full executable path to each of these using pyenv which, e.g. pyenv which python2.5 (should display $(pyenv root)/versions/2.5/bin/python2.5), or pyenv which python3.4 (should display path to system Python3). You can also specify multiple versions in a .python-version file, separated by newlines or any whitespace. hy

  Locating the Python Installation
Once pyenv has determined which version of Python your application has specified, it passes the command along to the corresponding Python installation.

Each Python version is installed into its own directory under
$(pyenv root)/versions.

For example, you might have these versions installed:

•   $(pyenv root)/versions/2.7.8/

•   $(pyenv root)/versions/3.4.2/

•   $(pyenv root)/versions/pypy-2.4.0/

As far as pyenv is concerned, version names are simply the directories in $(pyenv root)/versions.

  Managing Virtual Environments
There is a pyenv plugin named pyenv-virtualenv which comes with various features to help pyenv users to manage virtual environments created by virtualenv or Anaconda. Because the activate script of those virtual environments are relying on mutating $PATH variable of user's interactive shell, it will intercept pyenv's shim style command execution hooks. We'd recommend to install pyenv-virtualenv as well if you have some plan to play with those virtual environments.

Advanced Configuration
Skip this section unless you must know what every line in your shell profile is doing.

pyenv init is the only command that crosses the line of loading extra commands into your shell. Coming from rvm, some of you might be opposed to this idea. Here's what pyenv init actually does:

1.  Sets up your shims path. This is the only requirement for pyenv to function properly. You can do this by hand by prepending $(pyenv root)/shims to your $PATH.

2.  Rehashes shims. From time to time you'll need to rebuild your shim files. Doing this on init makes sure everything is up to date. You can always run pyenv rehash manually. You can disable this functionality by adding --no-rehash to the end of your pyenv init command line.

3.  Installs the sh dispatcher. This bit is also optional, but allows pyenv and plugins to change variables in your current shell, making commands like pyenv shell possible. The sh dispatcher doesn't do anything crazy like override cd or hack your shell prompt, but if for some reason you need pyenv to be a real script rather than a shell function, you can safely skip it.

To see exactly what happens under the hood for yourself, run "pyenv init -".

Uninstalling Python Versions
As time goes on, you will accumulate Python versions in your $(pyenv root)/versions directory.

To remove old Python versions, pyenv uninstall command to automate the removal process.

Alternatively, simply rm -rf the directory of the version you want to remove. You can find the directory of a particular Python version with the pyenv prefix command,

e.g. pyenv prefix 2.6.8.

Command Reference

The most common subcommands are:

  pyenv commands
Lists all available pyenv commands.

  pyenv local
Sets a local application-specific Python version by writing the version name to a .python-version file in the current directory. This version overrides the global version, and can be overridden itself by setting the PYENV_VERSION environment variable or with the pyenv shell command.

    $ pyenv local 2.7.6

When run without a version number, pyenv local reports the currently configured local version. You can also unset the local version:

    $ pyenv local --unset

Previous versions of pyenv stored local version specifications in a file named .pyenv-version. For backwards compatibility, pyenv will read a local version specified in an .pyenv-version file, but a .python-version file in the same directory will take precedence.

You can specify multiple versions as local Python at once.

Let's say if you have two versions of 2.7.6 and 3.3.3. If you prefer 2.7.6 over 3.3.3,

    $ pyenv local 2.7.6 3.3.3
    $ pyenv versions
      system
    * 2.7.6 (set by /Users/yyuu/path/to/project/.python-version)
    * 3.3.3 (set by /Users/yyuu/path/to/project/.python-version)
    $ python --version
    Python 2.7.6
    $ python2.7 --version
    Python 2.7.6
    $ python3.3 --version
    Python 3.3.3

or, if you prefer 3.3.3 over 2.7.6,

    $ pyenv local 3.3.3 2.7.6
    $ pyenv versions
      system
    * 2.7.6 (set by /Users/yyuu/path/to/project/.python-version)
    * 3.3.3 (set by /Users/yyuu/path/to/project/.python-version)
      venv27
    $ python --version
    Python 3.3.3
    $ python2.7 --version
    Python 2.7.6
    $ python3.3 --version
    Python 3.3.3

  pyenv global
Sets the global version of Python to be used in all shells by writing the version name to the ~/.pyenv/version file. This version can be overridden by an application-specific .python-version file, or by setting the PYENV_VERSION environment variable.

    $ pyenv global 2.7.6

The special version name system tells pyenv to use the system Python (detected by searching your $PATH).

When run without a version number, pyenv global reports the currently configured global version.

You can specify multiple versions as global Python at once.

Let's say if you have two versions of 2.7.6 and 3.3.3. If you prefer 2.7.6 over 3.3.3,

    $ pyenv global 2.7.6 3.3.3
    $ pyenv versions
      system
    * 2.7.6 (set by /Users/yyuu/.pyenv/version)
    * 3.3.3 (set by /Users/yyuu/.pyenv/version)
    $ python --version
    Python 2.7.6
    $ python2.7 --version
    Python 2.7.6
    $ python3.3 --version
    Python 3.3.3

or, if you prefer 3.3.3 over 2.7.6,

    $ pyenv global 3.3.3 2.7.6
    $ pyenv versions
      system
    * 2.7.6 (set by /Users/yyuu/.pyenv/version)
    * 3.3.3 (set by /Users/yyuu/.pyenv/version)
      venv27
    $ python --version
    Python 3.3.3
    $ python2.7 --version
    Python 2.7.6
    $ python3.3 --version
    Python 3.3.3

  pyenv shell
Sets a shell-specific Python version by setting the PYENV_VERSION environment variable in your shell. This version overrides application-specific versions and the global version.

    $ pyenv shell pypy-2.2.1

When run without a version number, pyenv shell reports the current value of PYENV_VERSION. You can also unset the shell version:

    $ pyenv shell --unset

Note that you'll need pyenv's shell integration enabled (step 3 of the installation instructions) in order to use this command. If you prefer not to use shell integration, you may simply set the PYENV_VERSION variable yourself:

    $ export PYENV_VERSION=pypy-2.2.1

You can specify multiple versions via PYENV_VERSION at once.

Let's say if you have two versions of 2.7.6 and 3.3.3. If you prefer 2.7.6 over 3.3.3,

    $ pyenv shell 2.7.6 3.3.3
    $ pyenv versions
      system
    * 2.7.6 (set by PYENV_VERSION environment variable)
    * 3.3.3 (set by PYENV_VERSION environment variable)
    $ python --version
    Python 2.7.6
    $ python2.7 --version
    Python 2.7.6
    $ python3.3 --version
    Python 3.3.3

or, if you prefer 3.3.3 over 2.7.6,

    $ pyenv shell 3.3.3 2.7.6
    $ pyenv versions
      system
    * 2.7.6 (set by PYENV_VERSION environment variable)
    * 3.3.3 (set by PYENV_VERSION environment variable)
      venv27
    $ python --version
    Python 3.3.3
    $ python2.7 --version
    Python 2.7.6
    $ python3.3 --version
    Python 3.3.3

  pyenv install
Install a Python version

    Usage: pyenv install [-f] [-kvp] <version>
           pyenv install [-f] [-kvp] <definition-file>
           pyenv install -l|--list
      -l, --list             List all available versions
      -f, --force            Install even if the version appears to be installed
      					already
      -s, --skip-existing    Skip the installation if the version appears to be
      					installed already
      python-build options:
      -k, --keep        Keep source tree in $PYENV_BUILD_ROOT after installation
                        (defaults to $PYENV_ROOT/sources)
      -v, --verbose     Verbose mode: print compilation status to stdout
      -p, --patch       Apply a patch from stdin before building
      -g, --debug       Build a debug version

To list the all available versions of Python, including Anaconda, Jython, pypy, and stackless, use:

    $ pyenv install --list

Then install the desired versions:

    $ pyenv install 2.7.6
    $ pyenv install 2.6.8
    $ pyenv versions
      system
      2.6.8
    * 2.7.6 (set by /home/yyuu/.pyenv/version)

  pyenv uninstall
Uninstall Python versions.

    Usage: pyenv uninstall [-f|--force] <version> ...
       -f  Attempt to remove the specified version without prompting
           for confirmation. If the version does not exist, do not
           display an error message.

  pyenv rehash
Installs shims for all Python binaries known to pyenv (i.e., ~/.pyenv/versions/*/bin/*). Run this command after you install a new version of Python, or install a package that provides binaries.

    $ pyenv rehash

  pyenv version
Displays the currently active Python version, along with information on how it was set.

    $ pyenv version
    2.7.6 (set by /home/yyuu/.pyenv/version)

  pyenv versions
Lists all Python versions known to pyenv, and shows an asterisk next to the currently active version.

    $ pyenv versions
      2.5.6
      2.6.8
    * 2.7.6 (set by /home/yyuu/.pyenv/version)
      3.3.3
      jython-2.5.3
      pypy-2.2.1

  pyenv which
Displays the full path to the executable that pyenv will invoke when you run the given command.

    $ pyenv which python3.3
    /home/yyuu/.pyenv/versions/3.3.3/bin/python3.3

  pyenv whence
Lists all Python versions with the given command installed.

    $ pyenv whence 2to3
    2.6.8
    2.7.6
    3.3.3

Environment variables
You can affect how pyenv operates with the following settings:

name (default)
    description

PYENV_VERSION
    Specifies the Python version to be used. Also see pyenv shell

PYENV_ROOT (~/.pyenv)
    Defines the directory under which Python versions and shims reside. Also see pyenv root

PYENV_DEBUG
    Outputs debug information.
    Also as: pyenv --debug <subcommand>

PYENV_HOOK_PATH
    Colon-separated list of paths searched for pyenv hooks.

PYENV_DIR ($PWD)
    Directory to start searching for .python-version files.

HTTP_PROXY,HTTPS_PROXY
    Proxy Variables

CONFIGURE_OPTS
    Pass configure options to build.

PYTHON_BUILD_ARIA2_OPTS
    Used to pass additional parameters to aria2 https://aria2.github.io/ If the aria2c binary is available on PATH, pyenv uses aria2c instead of curl or wget to download the Python Source code. If you have an unstable internet connection, you can use this variable to instruct aria2 to accelerate the download. In most cases, you will only need to use -x 10 -k 1M as value to PYTHON_BUILD_ARIA2_OPTS environment variable

License
The MIT License