Installing Packages¶

Requirements for Installing Packages¶

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

1. Install pip and setuptools: [3]

   If you have a PEP453-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 section below for details):

   Using 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 packages 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 packages 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: virtualenv and pyvenv. pyvenv is only available in Python 3.3 & 3.4, and only in Python 3.4, is pip & setuptools installed into environments by default, whereas virtualenv supports Python 2.6 thru Python 3.4 and pip & setuptools are installed by default in every version.

The basic usage is like so:

Using 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¶

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 pip vs easy_install breakdown in the Advanced Topics section.

Installing from PyPI¶

The most common usage of pip is to install from the Python Package Index using a requirement specifier. Generally speaking, a requirement specifier is composed of a project name followed by an optional version specifier. PEP440 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¶

Wheel is a pre-built distribution format that provides faster installation compared to Source Distributions (sdist), especially when a project contains compiled extensions.

As of v1.5, pip prefers wheels over sdists when searching indexes.

Although wheels are becoming more common on PyPI, if you want all of your dependencies converted to wheel, do the following (assuming you’re using a Requirements File):

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

Wheel is intended to replace Eggs. For a detailed comparison, see Wheel vs Egg.

Installing to the User Site¶

To install packages 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 Requirements File.

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 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 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 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