Drawing and plotting routines for IGraph.
igraph has two plotting backends at the moment: Cairo and Matplotlib.
The Cairo backend is dependent on the pycairo or cairocffi libraries that provide Python bindings to the popular Cairo library. This means that if you don't have pycairo or cairocffi installed, you won't be able to use the Cairo plotting backend. Whenever the documentation refers to the pycairo library, you can safely replace it with cairocffi as the two are API-compatible.
The Matplotlib backend uses the Matplotlib library. You will need to install it from PyPI if you want to use the Matplotlib plotting backend.
If you do not want to (or cannot) install any of the dependencies outlined above, you can still save the graph to an SVG file and view it from Mozilla Firefox (free) or edit it in Inkscape (free), Skencil (formerly known as Sketch, also free) or Adobe Illustrator.