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Tutorial on Installing Packages

Page Status:Incomplete
Last Reviewed:2014-12-24

This tutorial covers the basics of how to install Python :term:`packages <Distribution Package>`.

It's important to note that the term "package" in this context is being used as a synonym for a :term:`distribution <Distribution Package>` (i.e. a bundle of software to be installed), not to refer to the kind of :term:`package <Import Package>` that you import in your Python source code (i.e. a container of modules). It is common in the Python community to refer to a :term:`distribution <Distribution Package>` using the term "package". Using the term "distribution" is often not preferred, because it can easily be confused with a Linux distribution, or another larger software distribution like Python itself.

Contents

Requirements for Installing Packages

This section describes the steps to follow before installing other Python packages.

  1. Install :ref:`pip` and :ref:`setuptools`: [3]

    If you have a :ref:`PEP453 <pypa:PEP453s>`-compliant Python 3.4, it may already have the pip command available by default (and setuptools will be installed as well), or it may at least contain a working ensurepip. To install pip (and setuptools) using ensurepip, run: python -m ensurepip --upgrade.

    Otherwise:

    • Securely Download get-pip.py [1]
    • Run python get-pip.py. This will install or upgrade pip. Additionally, it will install setuptools if it's not installed already. To upgrade an existing setuptools, run pip install -U setuptools [2]

  2. Optionally, Create a virtual environment (See :ref:`section below <Creating and using Virtual Environments>` for details):

    Using :ref:`virtualenv`:

    pip install virtualenv
virtualenv <DIR>
source <DIR>/bin/activate

    Using pyvenv: [4]

    pyvenv <DIR>
source <DIR>/bin/activate

Creating Virtual Environments

Python "Virtual Environments" allow Python :term:`packages <Distribution Package>` to be installed in an isolated location for a particular application, rather than being installed globally.

Imagine you have an application that needs version 1 of LibFoo, but another application requires version 2. How can you use both these applications? If you install everything into /usr/lib/python2.7/site-packages (or whatever your platform’s standard location is), it’s easy to end up in a situation where you unintentionally upgrade an application that shouldn’t be upgraded.

Or more generally, what if you want to install an application and leave it be? If an application works, any change in its libraries or the versions of those libraries can break the application.

Also, what if you can’t install :term:`packages <Distribution Package>` into the global site-packages directory? For instance, on a shared host.

In all these cases, virtual environments can help you. They have their own installation directories and they don’t share libraries with other virtual environments.

Currently, there are two viable tools for creating Python virtual environments: :ref:`virtualenv` and pyvenv. pyvenv is only available in Python 3.3 & 3.4, and only in Python 3.4, is :ref:`pip` & :ref:`setuptools` installed into environments by default, whereas :ref:`virtualenv` supports Python 2.6 thru Python 3.4 and :ref:`pip` & :ref:`setuptools` are installed by default in every version.

The basic usage is like so:

Using :ref:`virtualenv`:

virtualenv <DIR>
source <DIR>/bin/activate

Using pyvenv:

pyvenv <DIR>
source <DIR>/bin/activate

For more information, see the virtualenv docs or the pyvenv docs.

Use pip for Installing

:ref:`pip` is the recommended installer. Below, we'll cover the most common usage scenarios. For more detail, see the pip docs, which includes a complete Reference Guide.

There are a few cases where you might want to use easy_install instead of pip. For details, see the the :ref:`pip vs easy_install` breakdown in the :doc:`Advanced Topics <additional>` section.

Installing from PyPI

The most common usage of :ref:`pip` is to install from the :term:`Python Package Index <Python Package Index (PyPI)>` using a :term:`requirement specifier <Requirement Specifier>`. Generally speaking, a requirement specifier is composed of a project name followed by an optional :term:`version specifier <Version Specifier>`. :ref:`PEP440 <pypa:PEP440s>` contains a full specification of the currently supported specifiers. Below are some examples.

To install the latest version of "SomeProject":

pip install 'SomeProject'

To install a specific version:

pip install 'SomeProject==1.4'

To install greater than or equal to one version and less than another:

pip install 'SomeProject>=1,<2'

To install a version that's "compatible" with a certain version: [5]

pip install 'SomeProject~=1.4.2'

In this case, this means to install any version "==1.4.*" version that's also ">=1.4.2".

Upgrading packages

Upgrade an already installed SomeProject to the latest from PyPI.

pip install --upgrade SomeProject

Installing Cached Wheels

:term:`Wheel` is a pre-built :term:`distribution <Distribution Package>` format that provides faster installation compared to :term:`Source Distributions (sdist) <Source Distribution (or "sdist")>`, especially when a project contains compiled extensions.

As of v1.5, :ref:`pip` prefers :term:`wheels <Wheel>` over :term:`sdists <Source Distribution (or "sdist")>` when searching indexes.

Although wheels are becoming more common on :term:`PyPI <Python Package Index (PyPI)>`, if you want all of your dependencies converted to wheel, do the following (assuming you're using a :ref:`Requirements File <pip:Requirements Files>`):

pip wheel --wheel-dir=/local/wheels -r requirements.txt

And then to install those requirements just using your local directory of wheels (and not from PyPI):

pip install --no-index --find-links=/local/wheels -r requirements.txt

:term:`Wheel` is intended to replace :term:`Eggs <Egg>`. For a detailed comparison, see :ref:`Wheel vs Egg`.

Installing to the User Site

To install :term:`packages <Distribution Package>` that are isolated to the current user, use the --user flag:

pip install --user SomeProject

For more information see the User Installs section from the pip docs.

Requirements files

Install a list of requirements specified in a :ref:`Requirements File <pip:Requirements Files>`.

pip install -r requirements.txt

Installing from VCS

Install a project from VCS in "editable" mode. For a full breakdown of the syntax, see pip's section on :ref:`VCS Support <pip:VCS Support>`.

pip install -e git+https://git.repo/some_pkg.git#egg=SomeProject          # from git
pip install -e hg+https://hg.repo/some_pkg.git#egg=SomeProject            # from mercurial
pip install -e svn+svn://svn.repo/some_pkg/trunk/#egg=SomeProject         # from svn
pip install -e git+https://git.repo/some_pkg.git@feature#egg=SomeProject  # from a branch

Installing from other Indexes

Install from an alternate index

pip install --index-url http://my.package.repo/simple/ SomeProject

Search an additional index during install, in addition to :term:`PyPI <Python Package Index (PyPI)>`

pip install --extra-index-url http://my.package.repo/simple SomeProject

Installing from a local src tree

Installing from local src in Development Mode, i.e. in such a way that the project appears to be installed, but yet is still editable from the src tree.

pip install -e <path>

You can also normally from src

pip install <path>

Installing from local archives

Install a particular source archive file.

pip install ./downloads/SomeProject-1.0.4.tar.gz

Install from a local directory containing archives (and don't check :term:`PyPI <Python Package Index (PyPI)>`)

pip install --no-index --find-links=file:///local/dir/ SomeProject
pip install --no-index --find-links=/local/dir/ SomeProject
pip install --no-index --find-links=relative/dir/ SomeProject

Installing Prereleases

Find pre-release and development versions, in addition to stable versions. By default, pip only finds stable versions.

pip install --pre SomeProject

Installing Setuptools "Extras"

Install setuptools extras.

$ pip install SomePackage[PDF]
$ pip install SomePackage[PDF]==3.0
$ pip install -e .[PDF]==3.0  # editable project in current directory
[1]"Secure" in this context means using a modern browser or a tool like curl that verifies SSL certificates when downloading from https URLs.
[2]Depending on your platform, this may require root or Administrator access. :ref:`pip` is currently considering changing this by making user installs the default behavior.
[3]On Linux and OSX, pip and setuptools will usually be available for the system python from a system package manager (e.g. yum or apt-get for linux, or homebrew for OSX). Unfortunately, there is often delay in getting the latest version this way, so in most cases, you'll want to use these instructions.
[4]Beginning with Python 3.4, pyvenv (a stdlib alternative to :ref:`virtualenv`) will create virtualenv environments with pip pre-installed, thereby making it an equal alternative to :ref:`virtualenv`.
[5]The compatible release specifier was accepted in :ref:`PEP440 <pypa:PEP440s>` and support was released in :ref:`setuptools` v8.0 and :ref:`pip` v6.0