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:
- Ggraph
The graph to test.
- Returns:
- bbool
A boolean that is True if
G
is a tree.
- Raises:
- NetworkXPointlessConcept
If
G
is empty.
See also
Notes
In another convention, a directed tree is known as a polytree and then tree corresponds to an arborescence.
Examples
>>> G = nx.Graph() >>> G.add_edges_from([(1, 2), (1, 3), (2, 4), (2, 5)]) >>> nx.is_tree(G) # n-1 edges True >>> G.add_edge(3, 4) >>> nx.is_tree(G) # n edges False