topological_sort¶

topological_sort(G, nbunch=None, reverse=False)[source]¶

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

reverse : bool, optional

Return postorder instead of preorder if True. Reverse mode is a bit more efficient.

Raises :

NetworkXError

Topological sort is defined for directed graphs only. If the graph G is undirected, a NetworkXError is raised.

NetworkXUnfeasible

If G is not a directed acyclic graph (DAG) no topological sort exists and a NetworkXUnfeasible exception is raised.