8.1.4. networkx.algorithms.dag.lexicographical_topological_sort¶

networkx.algorithms.dag.lexicographical_topological_sort(G, key=None)[source]¶

Return a generator of nodes in lexicographically topologically sorted 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

key : function, optional

This function maps nodes to keys with which to resolve ambiguities in the sort order. Defaults to the identity function.

Returns:

lexicographically_topologically_sorted_nodes : iterable

An iterable of node names in lexicographical topological sort order.

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. This can also be raised if G is changed while the returned iterator is being processed.

RuntimeError

If G is changed while the returned iterator is being processed.