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Removing an extra comma in "There are some systems, where the", and adding another "the" to "toward the end of shell configuration file".
370 lines
14 KiB
Markdown
370 lines
14 KiB
Markdown
# Simple Python Version Management: pyenv
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[](https://gitter.im/yyuu/pyenv?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
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[](https://travis-ci.org/yyuu/pyenv)
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pyenv lets you easily switch between multiple versions of Python. It's
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simple, unobtrusive, and follows the UNIX tradition of single-purpose
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tools that do one thing well.
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This project was forked from [rbenv](https://github.com/sstephenson/rbenv) and
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[ruby-build](https://github.com/sstephenson/ruby-build), and modified for Python.
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<img src="https://i.gyazo.com/699a58927b77e46e71cd674c7fc7a78d.png" width="735" height="490" />
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### pyenv _does..._
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* Let you **change the global Python version** on a per-user basis.
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* Provide support for **per-project Python versions**.
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* Allow you to **override the Python version** with an environment
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variable.
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* Search commands from **multiple versions of Python at a time**.
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This may be helpful to test across Python versions with [tox](http://pypi.python.org/pypi/tox).
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### In contrast with pythonbrew and pythonz, pyenv _does not..._
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* **Depend on Python itself.** pyenv was made from pure shell scripts.
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There is no bootstrap problem of Python.
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* **Need to be loaded into your shell.** Instead, pyenv's shim
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approach works by adding a directory to your `$PATH`.
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* **Manage virtualenv.** Of course, you can create [virtualenv](http://pypi.python.org/pypi/virtualenv)
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yourself, or [pyenv-virtualenv](https://github.com/yyuu/pyenv-virtualenv)
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to automate the process.
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----
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## Table of Contents
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* **[How It Works](#how-it-works)**
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* [Understanding PATH](#understanding-path)
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* [Understanding Shims](#understanding-shims)
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* [Choosing the Python Version](#choosing-the-python-version)
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* [Locating the Python Installation](#locating-the-python-installation)
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* **[Installation](#installation)**
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* [Basic GitHub Checkout](#basic-github-checkout)
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* [Upgrading](#upgrading)
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* [Homebrew on Mac OS X](#homebrew-on-mac-os-x)
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* [Advanced Configuration](#advanced-configuration)
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* [Uninstalling Python Versions](#uninstalling-python-versions)
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* **[Command Reference](#command-reference)**
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* **[Development](#development)**
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* [Version History](#version-history)
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* [License](#license)
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----
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## How It Works
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At a high level, pyenv intercepts Python commands using shim
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executables injected into your `PATH`, determines which Python version
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has been specified by your application, and passes your commands along
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to the correct Python installation.
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### Understanding PATH
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When you run a command like `python` or `pip`, your operating system
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searches through a list of directories to find an executable file with
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that name. This list of directories lives in an environment variable
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called `PATH`, with each directory in the list separated by a colon:
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/usr/local/bin:/usr/bin:/bin
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Directories in `PATH` are searched from left to right, so a matching
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executable in a directory at the beginning of the list takes
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precedence over another one at the end. In this example, the
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`/usr/local/bin` directory will be searched first, then `/usr/bin`,
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then `/bin`.
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### Understanding Shims
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pyenv works by inserting a directory of _shims_ at the front of your
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`PATH`:
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~/.pyenv/shims:/usr/local/bin:/usr/bin:/bin
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Through a process called _rehashing_, pyenv maintains shims in that
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directory to match every Python command across every installed version
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of Python—`python`, `pip`, and so on.
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Shims are lightweight executables that simply pass your command along
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to pyenv. So with pyenv installed, when you run, say, `pip`, your
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operating system will do the following:
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* Search your `PATH` for an executable file named `pip`
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* Find the pyenv shim named `pip` at the beginning of your `PATH`
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* Run the shim named `pip`, which in turn passes the command along to
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pyenv
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### Choosing the Python Version
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When you execute a shim, pyenv determines which Python version to use by
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reading it from the following sources, in this order:
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1. The `PYENV_VERSION` environment variable (if specified). You can use
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the [`pyenv shell`](https://github.com/yyuu/pyenv/blob/master/COMMANDS.md#pyenv-shell) command to set this environment
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variable in your current shell session.
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2. The application-specific `.python-version` file in the current
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directory (if present). You can modify the current directory's
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`.python-version` file with the [`pyenv local`](https://github.com/yyuu/pyenv/blob/master/COMMANDS.md#pyenv-local)
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command.
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3. The first `.python-version` file found (if any) by searching each parent
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directory, until reaching the root of your filesystem.
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4. The global `~/.pyenv/version` file. You can modify this file using
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the [`pyenv global`](https://github.com/yyuu/pyenv/blob/master/COMMANDS.md#pyenv-global) command. If the global version
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file is not present, pyenv assumes you want to use the "system"
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Python. (In other words, whatever version would run if pyenv weren't in your
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`PATH`.)
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**NOTE:** You can activate multiple versions at the same time, including multiple
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versions of Python2 or Python3 simultaneously. This allows for parallel usage of
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Python2 and Python3, and is required with tools like `tox`. For example, to set
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your path to first use your `system` Python and Python3 (set to 2.7.9 and 3.4.2
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in this example), but also have Python 3.3.6, 3.2, and 2.5 available on your
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`PATH`, one would first `pyenv install` the missing versions, then set `pyenv
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global system 3.3.6 3.2 2.5`. At this point, one should be able to find the full
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executable path to each of these using `pyenv which`, e.g. `pyenv which python2.5`
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(should display `$PYENV_ROOT/versions/2.5/bin/python2.5`), or `pyenv which
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python3.4` (should display path to system Python3).
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### Locating the Python Installation
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Once pyenv has determined which version of Python your application has
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specified, it passes the command along to the corresponding Python
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installation.
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Each Python version is installed into its own directory under
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`~/.pyenv/versions`.
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For example, you might have these versions installed:
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* `~/.pyenv/versions/2.7.8/`
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* `~/.pyenv/versions/3.4.2/`
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* `~/.pyenv/versions/pypy-2.4.0/`
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As far as pyenv is concerned, version names are simply the directories in
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`~/.pyenv/versions`.
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----
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## Installation
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If you're on Mac OS X, consider [installing with Homebrew](#homebrew-on-mac-os-x).
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### The automatic installer
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Visit my other project:
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https://github.com/yyuu/pyenv-installer
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### Basic GitHub Checkout
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This will get you going with the latest version of pyenv and make it
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easy to fork and contribute any changes back upstream.
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1. **Check out pyenv where you want it installed.**
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A good place to choose is `$HOME/.pyenv` (but you can install it somewhere else).
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$ git clone https://github.com/yyuu/pyenv.git ~/.pyenv
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2. **Define environment variable `PYENV_ROOT`** to point to the path where
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pyenv repo is cloned and add `$PYENV_ROOT/bin` to your `$PATH` for access
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to the `pyenv` command-line utility.
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$ echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bash_profile
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$ echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bash_profile
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**Zsh note**: Modify your `~/.zshenv` file instead of `~/.bash_profile`.
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**Ubuntu note**: Modify your `~/.bashrc` file instead of `~/.bash_profile`.
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3. **Add `pyenv init` to your shell** to enable shims and autocompletion.
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Please make sure `eval "$(pyenv init -)"` is placed toward the end of the shell
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configuration file since it manipulates `PATH` during the initialization.
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$ echo 'eval "$(pyenv init -)"' >> ~/.bash_profile
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**Zsh note**: Modify your `~/.zshenv` file instead of `~/.bash_profile`.
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**Ubuntu note**: Modify your `~/.bashrc` file instead of `~/.bash_profile`.
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**General warning**: There are some systems where the `BASH_ENV` variable is configured
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to point to `.bashrc`. On such systems you should almost certainly put the abovementioned line
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`eval "$(pyenv init -)` into `.bash_profile`, and **not** into `.bashrc`. Otherwise you
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may observe strange behaviour, such as `pyenv` getting into an infinite loop.
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See [#264](https://github.com/yyuu/pyenv/issues/264) for details.
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4. **Restart your shell so the path changes take effect.**
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You can now begin using pyenv.
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$ exec $SHELL
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5. **Install Python versions into `$PYENV_ROOT/versions`.**
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For example, to download and install Python 2.7.8, run:
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$ pyenv install 2.7.8
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**NOTE:** If you need to pass configure option to build, please use
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```CONFIGURE_OPTS``` environment variable.
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**NOTE:** If you want to use proxy to download, please use `http_proxy` and `https_proxy`
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environment variable.
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**NOTE:** If you are having trouble installing a python version,
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please visit the wiki page about
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[Common Build Problems](https://github.com/yyuu/pyenv/wiki/Common-build-problems)
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6. **Rebuild the shim binaries.**
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You should do this any time you install a new Python binary.
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(Examples: installing a new Python version, or installing a package that provides a binary.)
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$ pyenv rehash
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This can be automated for pip using
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[pyenv-pip-rehash](https://github.com/yyuu/pyenv-pip-rehash), which invokes
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`pyenv rehash` after (un)installing packages using pip.
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#### Upgrading
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If you've installed pyenv using the instructions above, you can
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upgrade your installation at any time using git.
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To upgrade to the latest development version of pyenv, use `git pull`:
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$ cd ~/.pyenv
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$ git pull
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To upgrade to a specific release of pyenv, check out the corresponding tag:
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$ cd ~/.pyenv
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$ git fetch
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$ git tag
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v0.1.0
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$ git checkout v0.1.0
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### Homebrew on Mac OS X
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You can also install pyenv using the [Homebrew](http://brew.sh)
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package manager for Mac OS X.
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$ brew update
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$ brew install pyenv
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To upgrade pyenv in the future, use `upgrade` instead of `install`.
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After installation, you'll need to add `eval "$(pyenv init -)"` to your profile (as stated in the caveats displayed by Homebrew — to display them again, use `brew info pyenv`). You only need to add that to your profile once.
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Then follow the rest of the post-installation steps under "Basic GitHub Checkout" above, starting with #4 ("restart your shell so the path changes take effect").
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### Advanced Configuration
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Skip this section unless you must know what every line in your shell
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profile is doing.
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`pyenv init` is the only command that crosses the line of loading
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extra commands into your shell. Coming from rvm, some of you might be
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opposed to this idea. Here's what `pyenv init` actually does:
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1. **Sets up your shims path.** This is the only requirement for pyenv to
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function properly. You can do this by hand by prepending
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`~/.pyenv/shims` to your `$PATH`.
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2. **Installs autocompletion.** This is entirely optional but pretty
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useful. Sourcing `~/.pyenv/completions/pyenv.bash` will set that
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up. There is also a `~/.pyenv/completions/pyenv.zsh` for Zsh
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users.
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3. **Rehashes shims.** From time to time you'll need to rebuild your
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shim files. Doing this on init makes sure everything is up to
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date. You can always run `pyenv rehash` manually.
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4. **Installs the sh dispatcher.** This bit is also optional, but allows
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pyenv and plugins to change variables in your current shell, making
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commands like `pyenv shell` possible. The sh dispatcher doesn't do
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anything crazy like override `cd` or hack your shell prompt, but if
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for some reason you need `pyenv` to be a real script rather than a
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shell function, you can safely skip it.
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To see exactly what happens under the hood for yourself, run `pyenv init -`.
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### Uninstalling Python Versions
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As time goes on, you will accumulate Python versions in your
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`~/.pyenv/versions` directory.
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To remove old Python versions, `pyenv uninstall` command to automate
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the removal process.
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Alternatively, simply `rm -rf` the directory of the version you want
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to remove. You can find the directory of a particular Python version
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with the `pyenv prefix` command, e.g. `pyenv prefix 2.6.8`.
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----
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## Command Reference
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See [COMMANDS.md](COMMANDS.md).
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----
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## Development
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The pyenv source code is [hosted on GitHub](https://github.com/yyuu/pyenv).
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It's clean, modular, and easy to understand--even if you're not a shell hacker.
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Please feel free to submit Pull Requests and report bugs on the
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[issue tracker](https://github.com/yyuu/pyenv/issues).
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### Version History
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See [CHANGELOG.md](CHANGELOG.md).
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### License
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(The MIT license)
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* Copyright (c) 2013 Yamashita, Yuu
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* Copyright (c) 2013 Sam Stephenson
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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