Pynauty is a Python extension module to Brendan McKay's Nauty C procedures. The module provides Python classes to represent graphs and functions for isomorphism testing and computing automorphism groups of graphs. The graphs can be undirected or directed. They can contain loops but no multiple edges. There is always a vertex-coloring associated with them. Ordinary, that is not vertex-colored, graphs can be represented with all vertices having the same color. For download, documentation, installation instructions please visit: http://designtheory.org/software/pynauty/ -- , Peter Dobcsanyi