is_forest

is_forest(G)

Returns True if G is a forest.

A forest is a graph with no undirected cycles.

For directed graphs, G is a forest if the underlying graph is a forest. The underlying graph is obtained by treating each directed edge as a single undirected edge in a multigraph.

Parameters:

Ggraph

The graph to test.

Returns:

bbool

A boolean that is True if G is a forest.

Raises:

NetworkXPointlessConcept

If G is empty.

See also

is_branching

Notes

In another convention, a directed forest is known as a polyforest and then forest corresponds to a branching.

Examples

>>> G = nx.Graph()
>>> G.add_edges_from([(1, 2), (1, 3), (2, 4), (2, 5)])
>>> nx.is_forest(G)
True
>>> G.add_edge(4, 1)
>>> nx.is_forest(G)
False
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Additional backends implement this function

cugraph : GPU-accelerated backend.