Installing Python Modules¶
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As a popular open source development project, Python has an active supporting community of contributors and users that also make their software available for other Python developers to use under open source license terms.
This allows Python users to share and collaborate effectively, benefiting from the solutions others have already created to common (and sometimes even rare!) problems, as well as potentially contributing their own solutions to the common pool.
This guide covers the installation part of the process. For a guide to creating and sharing your own Python projects, refer to the Python packaging user guide.
Note
For corporate and other institutional users, be aware that many organisations have their own policies around using and contributing to open source software. Please take such policies into account when making use of the distribution and installation tools provided with Python.
Key terms¶
pipis the preferred installer program. Starting with Python 3.4, it is included by default with the Python binary installers.Avirtual environmentis a semi-isolated Python environment that allows packages to be installed for use by a particular application, rather than being installed system wide.
venvis the standard tool for creating virtual environments, and has been part of Python since Python 3.3. Starting with Python 3.4, it defaults to installingpipinto all created virtual environments.virtualenvis a third party alternative (and predecessor) tovenv.It allows virtual environments to be used on versions of Python prior to 3.4, which either don’t providevenvat all, or aren’t able to automatically installpipinto created environments.ThePython Package Indexis a public repository of open source licensed packages made available for use by other Python users.
thePython Packaging Authorityis the group of developers and documentation authors responsible for the maintenance and evolution of the standard packaging tools and the associated metadata and file format standards. They maintain a variety of tools, documentation, and issue trackers onGitHub.
distutilsis the original build and distribution system first added to the Python standard library in 1998. While direct use ofdistutilsis being phased out, it still laid the foundation for the current packaging and distribution infrastructure, and it not only remains part of the standard library, but its name lives on in other ways (such as the name of the mailing list used to coordinate Python packaging standards development).
Changed in version 3.5:The use ofvenvis now recommended for creating virtual environments.
Basic usage¶
The standard packaging tools are all designed to be used from the command line.
The following command will install the latest version of a module and its dependencies from the Python Package Index:
Python -m pip install SomePackage
Note
For POSIX users (including macOS and Linux users), the examples in this guide assume the use of avirtual environment.
For Windows users, the examples in this guide assume that the option to adjust the system PATH environment variable was selected when installing Python.
It’s also possible to specify an exact or minimum version directly on the
command line. When using comparator operators such as>,<or some other
special character which get interpreted by shell, the package name and the
version should be enclosed within double quotes:
Python -m pip install SomePackage==1.0.4 # specific version
Python -m pip install "SomePackage>=1.0.4" # minimum version
Normally, if a suitable module is already installed, attempting to install it again will have no effect. Upgrading existing modules must be requested explicitly:
Python -m pip install --upgrade SomePackage
More information and resources regardingpipand its capabilities can be
found in thePython Packaging User Guide.
Creation of virtual environments is done through thevenvmodule.
Installing packages into an active virtual environment uses the commands shown
above.
How do I…?¶
These are quick answers or links for some common tasks.
…installpipin versions of Python prior to Python 3.4?¶
Python only started bundlingpipwith Python 3.4. For earlier versions,
pipneeds to be “bootstrapped” as described in the Python Packaging
User Guide.
…install packages just for the current user?¶
Passing the--useroption toPython-mpipinstallwill install a
package just for the current user, rather than for all users of the system.
…install scientific Python packages?¶
A number of scientific Python packages have complex binary dependencies, and
aren’t currently easy to install usingpipdirectly. At this point in
time, it will often be easier for users to install these packages by
other means
rather than attempting to install them withpip.
…work with multiple versions of Python installed in parallel?¶
On Linux, macOS, and other POSIX systems, use the versioned Python commands
in combination with the-mswitch to run the appropriate copy of
pip:
Python 2 -m pip install SomePackage # default Python 2
Python 2.7 -m pip install SomePackage # specifically Python 2.7
Python 3 -m pip install SomePackage # default Python 3
Python 3.4 -m pip install SomePackage # specifically Python 3.4
Appropriately versionedpipcommands may also be available.
On Windows, use thepyPython launcher in combination with the-m
switch:
py -2 -m pip install SomePackage # default Python 2
py -2.7 -m pip install SomePackage # specifically Python 2.7
py -3 -m pip install SomePackage # default Python 3
py -3.4 -m pip install SomePackage # specifically Python 3.4
Common installation issues¶
Installing into the system Python on Linux¶
On Linux systems, a Python installation will typically be included as part
of the distribution. Installing into this Python installation requires
root access to the system, and may interfere with the operation of the
system package manager and other components of the system if a component
is unexpectedly upgraded usingpip.
On such systems, it is often better to use a virtual environment or a
per-user installation when installing packages withpip.
Pip not installed¶
It is possible thatpipdoes not get installed by default. One potential fix is:
Python -m ensurepip --default-pip
There are also additional resources forinstalling pip.
Installing binary extensions¶
Python has typically relied heavily on source based distribution, with end users being expected to compile extension modules from source as part of the installation process.
With the introduction of support for the binarywheelformat, and the
ability to publish wheels for at least Windows and macOS through the
Python Package Index, this problem is expected to diminish over time,
as users are more regularly able to install pre-built extensions rather
than needing to build them themselves.
Some of the solutions for installingscientific software
that are not yet available as pre-builtwheelfiles may also help with
obtaining other binary extensions without needing to build them locally.