networkx.topological_sort

topological_sort(G, nbunch=None)

Return a list of nodes in topological sort order.

A topological sort is a nonunique permutation of the nodes such that an edge from u to v implies that u appears before v in the topological sort order.

Parameters:

G : NetworkX digraph

A directed graph

nbunch : container of nodes (optional)

Explore graph in specified order given in nbunch

See also

is_directed_acyclic_graph

Notes

If G is not a directed acyclic graph (DAG) no topological sort exists and the Python keyword None is returned.

This algorithm is based on a description and proof in The Algorithm Design Manual [R91] .

References

[R91]

(1, 2) Skiena, S. S. The Algorithm Design Manual (Springer-Verlag, 1998). http://www.amazon.com/exec/obidos/ASIN/0387948600/ref=ase_thealgorithmrepo/