# networkx.algorithms.tree.recognition.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.