This chapter describes how to install the C core of |igraph| and its Python bindings on various operating systems.

|igraph| is primarily a library written in C. It is not a standalone program, nor it is a Python package that you can just drop on your Python path to start using it. Therefore, if you would like to exploit |igraph|'s functionality in Python, you must install a few packages. Do not worry, though, there are precompiled packages for the major operating systems, so you will not have to compile |igraph| from source unless you use an esoteric operating system or you have specific requirements (i.e., adding a custom patch to |igraph|'s C core). Precompiled packages are often called binary packages, while the raw source code is usually referred to as the source package.

In general, you should almost always opt for the binary package unless a binary package is not available for your platform or you have some local modifications that you want to incorporate into |igraph|'s source. Installation from a binary package tells you how to install |igraph| from a precompiled binary package on various platforms. Compiling igraph from source tells you how to compile |igraph| from the source package.

There is a Windows installer for |igraph|'s Python interface on the Python Package Index. Download the one that is suitable for your Python version (currently there are binary packages for Python 2.6, Python 2.7 and Python 3.2, though it might change in the future). To test the installed package, launch your favourite Python IDE and type the following:

>>> import igraph.test
>>> igraph.test.run_tests()

The above commands run the bundled test cases to ensure that everything is fine with your |igraph| installation.

Graph plotting in |igraph| is implemented using a third-party package called Cairo. If you want to create publication-quality plots in |igraph| on Windows, you must also install Cairo and its Python bindings. The Cairo project does not provide pre-compiled binaries for Windows, but Christoph Gohlke maintains a site containing unofficial Windows binaries for several Python extension packages, including Cairo itself. Therefore, the easiest way to install Cairo on Windows along with its Python bindings is simply to download it from Christoph's site. Make sure you use an installer that is suitable for your Windows platform (32-bit or 64-bit) and the version of Python you are using.

In case you use a version of Python for which the above site does not provide an installer, you can install it from an alternative source in a slightly more complicated way by following the steps below:

1. Get the latest PyCairo for Windows installer from http://ftp.gnome.org/pub/gnome/binaries/win32/pycairo/1.8. Make sure you grab the one that matches your Python version. At the time of writing, the above folder contained installers for Python 2.6 and 2.7 only. You may also try and go one level up, then down then 1.4 subfolder -- these are older versions, but they work with Python 2.5 and Python 2.6 as well.
2. Install PyCairo using the installer. The installer extracts the necessary files into Lib\site-packages\cairo within the folder where Python is installed. Unfortunately there are some extra DLLs which are required to make Cairo work, so we have to get these as well.
3. Head to http://ftp.gnome.org/pub/gnome/binaries/win32/dependencies/ and get the binary versions of Cairo (cairo_1.8.10-3_win32.zip at the time of writing), Fontconfig (fontconfig_2.8.0-2_win32.zip), Freetype (freetype_2.4.4-1_win32.zip), Expat (expat_2.0.1-1_win32.zip), libpng (libpng_1.4.3-1_win32.zip) and zlib (zlib_1.2.5-2_win32.zip). Version numbers may vary, so be adaptive! Each ZIP file will contain a bin subfolder with a DLL file in it. Put the following DLLs in Lib\site-packages\cairo within your Python installation:
   • freetype6.dll (from freetype_2.4.4-1_win32.zip)
   • libcairo-2.dll (from cairo_1.8.10-3_win32.zip)
   • libexpat-1.dll (from expat_2.0.1-1_win32.zip)
   • libfontconfig-1.dll (from fontconfig_2.8.0-2_win32.zip)
   • libpng14-14.dll (from libpng_1.4.3-1_win32.zip)
   • zlib1.dll (from zlib_1.2.5-2_win32.zip).

Having done that, you can launch Python again and check if it worked:

>>> from igraph import *
>>> g = Graph.Famous("petersen")
>>> plot(g)

Make sure you have all the required dependencies installed:

$ sudo apt install build-essential python-dev libxml2 libxml2-dev zlib1g-dev

and then install with pip / pip3

$ pip install python-igraph

There is a Mac OS X installer for |igraph|'s Python interface on the Python Package Index which works for Intel-based Macs running OS X Lion. The default Python version in Leopard is Python 2.7, so the package is compiled for this specific version. PowerPC users should compile the package themselves (see Compiling igraph from source). To test the installed package, launch your favourite Python IDE or the default command line interpreter and type the following:

>>> import igraph.test
>>> igraph.test.run_tests()

The above commands run the bundled test cases to ensure that everything is fine with your |igraph| installation.

Graph plotting in |igraph| is implemented using a third-party package called Cairo. If you want to create publication-quality plots in |igraph| on Mac OS X, you must also install Cairo and its Python bindings. The Cairo project does not provide pre-compiled binaries for Mac OS X, but MacPorts and Fink does, so you can use them to install Cairo. The Cairo homepage gives you some installation instructions. However, this is only one half of the job, you will also need the Python bindings of Cairo from the PyCairo homepage. At the moment there are no precompiled PyCairo packages for Mac OS X either.

TODO: detailed compilation instructions for PyCairo