Question

I read Python Patterns – Implementing Graphs. However this implementation is inefficient for getting the edges that point to a node.

In other languages a common solution is using a two-dimensional array, but to do this in Python would require a list of lists. This does not seem pythonic.

What is an implementation of a directed graph in python where finding all the nodes with edges to and from a node (as two separate lists) is fast?

Answer 1

Scipy offers efficient Graph routines if computational efficiency or scientific computing is your concern:

http://docs.scipy.org/doc/scipy/reference/sparse.csgraph.html