is_tree¶

is_tree(G)[source]¶

Returns True if G is a tree.

A tree is a connected graph with no undirected cycles.

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

Parameters:	G (graph) – The graph to test.
Returns:	b – A boolean that is `True` if `G` is a tree.
Return type:	bool

Notes

In another convention, a directed tree is known as a polytree and then tree corresponds to an arborescence.