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.
This project was forked from rbenv and ruby-build, and modified for Python.
$PATH
.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.
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
.
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 across every installed version
of Python—python
, pip
, and so on.
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:
PATH
for an executable file named pip
pip
at the beginning of your PATH
pip
, which in turn passes the command along to
pyenvWhen you execute a shim, pyenv determines which Python version to use by reading it from the following sources, in this order:
The PYENV_VERSION
environment variable (if specified). You can use
the pyenv shell
command to set this environment
variable in your current shell session.
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.
The first .python-version
file found (if any) by searching each parent
directory, until reaching the root of your filesystem.
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.
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
.
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.
For pyenv to install python correctly you should install the Python build dependencies.
brew update
brew install pyenv
pyenv init
to your shell to enable shims and autocompletion").If you're on Windows, consider using @kirankotari's pyenv-win
fork. (pyenv
does not work on windows outside the Windows Subsystem for Linux)
Visit my other project: https://github.com/pyenv/pyenv-installer
This will get you going with the latest version of pyenv and make it easy to fork and contribute any changes back upstream.
Check out pyenv where you want it installed.
A good place to choose is $HOME/.pyenv
(but you can install it somewhere else).
git clone https://github.com/pyenv/pyenv.git ~/.pyenv
Optionally, try to compile dynamic bash extension to speed up pyenv. Don't worry if it fails; pyenv will still work normally:
cd ~/.pyenv && src/configure && make -C src
Define environment variable PYENV_ROOT
to point to the path where
pyenv repo is cloned and add $PYENV_ROOT/bin
to your $PATH
for access
to the pyenv
command-line utility.
For bash:
echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bash_profile
echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bash_profile
For Ubuntu Desktop:
echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc
echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc
For Zsh:
echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.zshrc
echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.zshrc
For Fish shell:
set -Ux PYENV_ROOT $HOME/.pyenv
set -Ux fish_user_paths $PYENV_ROOT/bin $fish_user_paths
Proxy note: If you use a proxy, export http_proxy
and https_proxy
too.
Add pyenv init
to your shell to enable shims and autocompletion.
Please make sure eval "$(pyenv init -)"
is placed toward the end of the shell
configuration file since it manipulates PATH
during the initialization.
For bash:
echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n eval "$(pyenv init -)"\nfi' >> ~/.bash_profile
For Ubuntu Desktop and Fedora:
echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n eval "$(pyenv init -)"\nfi' >> ~/.bashrc
For Zsh:
echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n eval "$(pyenv init -)"\nfi' >> ~/.zshrc
For Fish shell:
echo -e '\n\n# pyenv init\nif command -v pyenv 1>/dev/null 2>&1\n pyenv init - | source\nend' >> ~/.config/fish/config.fish
General warning: There are some systems where the BASH_ENV
variable is configured
to point to .bashrc
. On such systems you should almost certainly put the above mentioned line
eval "$(pyenv init -)"
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.
Restart your shell so the path changes take effect. You can now begin using pyenv.
exec "$SHELL"
Install Python build dependencies before attempting to install a new Python version.
Install Python versions into $(pyenv root)/versions
.
For example, to download and install Python 2.7.8, run:
pyenv install 2.7.8
NOTE: If you need to pass configure option to build, please use
CONFIGURE_OPTS
environment variable.
NOTE: If you want to use proxy to download, please use http_proxy
and https_proxy
environment variable.
NOTE: If you are having trouble installing a python version, please visit the wiki page about Common Build Problems
If you've installed pyenv using homebrew, upgrade using:
brew upgrade pyenv
If you've installed pyenv using the instructions above, you can upgrade your installation at any time using git.
To upgrade to the latest development version of pyenv, use git pull
:
cd $(pyenv root)
git pull
To upgrade to a specific release of pyenv, check out the corresponding tag:
cd $(pyenv root)
git fetch
git tag
git checkout v0.1.0
The simplicity of pyenv makes it easy to temporarily disable it, or uninstall from the system.
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.
To completely uninstall pyenv, perform step (1) and then remove
its root directory. This will delete all Python versions that were
installed under $(pyenv root)/versions/
directory:
rm -rf $(pyenv root)
If you've installed pyenv using a package manager, as a final step perform the pyenv package removal. For instance, for Homebrew:
brew uninstall pyenv
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:
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
.
Installs autocompletion. This is entirely optional but pretty
useful. Sourcing $(pyenv root)/completions/pyenv.bash
will set that
up. There is also a $(pyenv root)/completions/pyenv.zsh
for Zsh
users.
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.
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 -
.
If you don't want to use pyenv init
and shims, you can still benefit
from pyenv's ability to install Python versions for you. Just run
pyenv install
and you will find versions installed in
$(pyenv root)/versions
, which you can manually execute or symlink
as required.
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
.
See COMMANDS.md.
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 |
see wiki | Colon-separated list of paths searched for pyenv hooks. |
PYENV_DIR |
$PWD |
Directory to start searching for .python-version files. |
PYTHON_BUILD_ARIA2_OPTS |
Used to pass additional parameters to aria2 .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 |
The pyenv source code is hosted on GitHub. It's clean, modular, and easy to understand, even if you're not a shell hacker.
Tests are executed using Bats:
bats test
bats/test/<file>.bats
Please feel free to submit pull requests and file bugs on the issue tracker.
See CHANGELOG.md.
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