Installing Python Modules (Legacy version)¶
The entire distutils package has been deprecated and will be removed in Python 3.12. This documentation is retained as a reference only, and will be removed with the package. See the What’s New entry for more information.
The up to date module installation documentation. For regular Python usage, you almost certainly want that document rather than this one.
This document is being retained solely until the setuptools documentation at https://setuptools.readthedocs.io/en/latest/setuptools.html independently covers all of the relevant information currently included here.
This guide only covers the basic tools for building and distributing extensions that are provided as part of this version of Python. Third party tools offer easier to use and more secure alternatives. Refer to the quick recommendations section in the Python Packaging User Guide for more information.
Introduction¶
In Python 2.0, the distutils API was first added to the standard library. This provided Linux distro maintainers with a standard way of converting Python projects into Linux distro packages, and system administrators with a standard way of installing them directly onto target systems.
In the many years since Python 2.0 was released, tightly coupling the build system and package installer to the language runtime release cycle has turned out to be problematic, and it is now recommended that projects use the pip package installer and the setuptools build system, rather than using distutils directly.
This legacy documentation is being retained only until we’re confident that the setuptools documentation covers everything needed.
Distutils based source distributions¶
If you download a module source distribution, you can tell pretty quickly if it was packaged and distributed in the standard way, i.e. using the Distutils. First, the distribution’s name and version number will be featured prominently in the name of the downloaded archive, e.g. foo-1.0.tar.gz or widget-0.9.7.zip . Next, the archive will unpack into a similarly named directory: foo-1.0 or widget-0.9.7 . Additionally, the distribution will contain a setup script setup.py , and a file named README.txt or possibly just README , which should explain that building and installing the module distribution is a simple matter of running one command from a terminal:
For Windows, this command should be run from a command prompt window ( Start ‣ Accessories ):
If all these things are true, then you already know how to build and install the modules you’ve just downloaded: Run the command above. Unless you need to install things in a non-standard way or customize the build process, you don’t really need this manual. Or rather, the above command is everything you need to get out of this manual.
Standard Build and Install¶
As described in section Distutils based source distributions , building and installing a module distribution using the Distutils is usually one simple command to run from a terminal:
Platform variations¶
You should always run the setup command from the distribution root directory, i.e. the top-level subdirectory that the module source distribution unpacks into. For example, if you’ve just downloaded a module source distribution foo-1.0.tar.gz onto a Unix system, the normal thing to do is:
gunzip -c foo-1.0.tar.gz | tar xf - # unpacks into directory foo-1.0 cd foo-1.0 python setup.py install
On Windows, you’d probably download foo-1.0.zip . If you downloaded the archive file to C:\Temp , then it would unpack into C:\Temp\foo-1.0 ; you can use either an archive manipulator with a graphical user interface (such as WinZip) or a command-line tool (such as unzip or pkunzip) to unpack the archive. Then, open a command prompt window and run:
cd c:\Temp\foo-1.0 python setup.py install
Splitting the job up¶
Running setup.py install builds and installs all modules in one run. If you prefer to work incrementally—especially useful if you want to customize the build process, or if things are going wrong—you can use the setup script to do one thing at a time. This is particularly helpful when the build and install will be done by different users—for example, you might want to build a module distribution and hand it off to a system administrator for installation (or do it yourself, with super-user privileges).
For example, you can build everything in one step, and then install everything in a second step, by invoking the setup script twice:
python setup.py build python setup.py install
If you do this, you will notice that running the install command first runs the build command, which—in this case—quickly notices that it has nothing to do, since everything in the build directory is up-to-date.
You may not need this ability to break things down often if all you do is install modules downloaded off the ‘net, but it’s very handy for more advanced tasks. If you get into distributing your own Python modules and extensions, you’ll run lots of individual Distutils commands on their own.
How building works¶
As implied above, the build command is responsible for putting the files to install into a build directory. By default, this is build under the distribution root; if you’re excessively concerned with speed, or want to keep the source tree pristine, you can change the build directory with the —build-base option. For example:
python setup.py build --build-base=/path/to/pybuild/foo-1.0
(Or you could do this permanently with a directive in your system or personal Distutils configuration file; see section Distutils Configuration Files .) Normally, this isn’t necessary.
The default layout for the build tree is as follows:
--- build/ --- lib/ or --- build/ --- lib./ temp./
where expands to a brief description of the current OS/hardware platform and Python version. The first form, with just a lib directory, is used for “pure module distributions”—that is, module distributions that include only pure Python modules. If a module distribution contains any extensions (modules written in C/C++), then the second form, with two directories, is used. In that case, the temp. plat directory holds temporary files generated by the compile/link process that don’t actually get installed. In either case, the lib (or lib. plat ) directory contains all Python modules (pure Python and extensions) that will be installed.
In the future, more directories will be added to handle Python scripts, documentation, binary executables, and whatever else is needed to handle the job of installing Python modules and applications.
How installation works¶
After the build command runs (whether you run it explicitly, or the install command does it for you), the work of the install command is relatively simple: all it has to do is copy everything under build/lib (or build/lib. plat ) to your chosen installation directory.
If you don’t choose an installation directory—i.e., if you just run setup.py install —then the install command installs to the standard location for third-party Python modules. This location varies by platform and by how you built/installed Python itself. On Unix (and macOS, which is also Unix-based), it also depends on whether the module distribution being installed is pure Python or contains extensions (“non-pure”):
Standard installation location
prefix /lib/python X.Y /site-packages
/usr/local/lib/python X.Y /site-packages
exec-prefix /lib/python X.Y /site-packages
/usr/local/lib/python X.Y /site-packages
C:\Python XY \Lib\site-packages
- Most Linux distributions include Python as a standard part of the system, so prefix and exec-prefix are usually both /usr on Linux. If you build Python yourself on Linux (or any Unix-like system), the default prefix and exec-prefix are /usr/local .
- The default installation directory on Windows was C:\Program Files\Python under Python 1.6a1, 1.5.2, and earlier.
prefix and exec-prefix stand for the directories that Python is installed to, and where it finds its libraries at run-time. They are always the same under Windows, and very often the same under Unix and macOS. You can find out what your Python installation uses for prefix and exec-prefix by running Python in interactive mode and typing a few simple commands. Under Unix, just type python at the shell prompt. Under Windows, choose Start ‣ Programs ‣ Python X.Y ‣ Python (command line) . Once the interpreter is started, you type Python code at the prompt. For example, on my Linux system, I type the three Python statements shown below, and get the output as shown, to find out my prefix and exec-prefix :
Python 2.4 (#26, Aug 7 2004, 17:19:02) Type "help", "copyright", "credits" or "license" for more information. >>> import sys >>> sys.prefix '/usr' >>> sys.exec_prefix '/usr'
A few other placeholders are used in this document: X.Y stands for the version of Python, for example 3.2 ; abiflags will be replaced by the value of sys.abiflags or the empty string for platforms which don’t define ABI flags; distname will be replaced by the name of the module distribution being installed. Dots and capitalization are important in the paths; for example, a value that uses python3.2 on UNIX will typically use Python32 on Windows.
If you don’t want to install modules to the standard location, or if you don’t have permission to write there, then you need to read about alternate installations in section Alternate Installation . If you want to customize your installation directories more heavily, see section Custom Installation on custom installations.
Alternate Installation¶
Often, it is necessary or desirable to install modules to a location other than the standard location for third-party Python modules. For example, on a Unix system you might not have permission to write to the standard third-party module directory. Or you might wish to try out a module before making it a standard part of your local Python installation. This is especially true when upgrading a distribution already present: you want to make sure your existing base of scripts still works with the new version before actually upgrading.
The Distutils install command is designed to make installing module distributions to an alternate location simple and painless. The basic idea is that you supply a base directory for the installation, and the install command picks a set of directories (called an installation scheme) under this base directory in which to install files. The details differ across platforms, so read whichever of the following sections applies to you.
Note that the various alternate installation schemes are mutually exclusive: you can pass —user , or —home , or —prefix and —exec-prefix , or —install-base and —install-platbase , but you can’t mix from these groups.
Alternate installation: the user scheme¶
This scheme is designed to be the most convenient solution for users that don’t have write permission to the global site-packages directory or don’t want to install into it. It is enabled with a simple option:
python setup.py install --user
Files will be installed into subdirectories of site.USER_BASE (written as userbase hereafter). This scheme installs pure Python modules and extension modules in the same location (also known as site.USER_SITE ). Here are the values for UNIX, including macOS:
userbase /lib/python X.Y /site-packages