union(G, H, rename=())[source]#

Combine graphs G and H. The names of nodes must be unique.

A name collision between the graphs will raise an exception.

A renaming facility is provided to avoid name collisions.

G, Hgraph

A NetworkX graph

renameiterable , optional

Node names of G and H can be changed by specifying the tuple rename=(‘G-‘,’H-’) (for example). Node “u” in G is then renamed “G-u” and “v” in H is renamed “H-v”.

UA union graph with the same type as G.


To combine graphs that have common nodes, consider compose(G, H) or the method, Graph.update().

disjoint_union() is similar to union() except that it avoids name clashes by relabeling the nodes with sequential integers.

Edge and node attributes are propagated from G and H to the union graph. Graph attributes are also propagated, but if they are present in both G and H, then the value from H is used.


>>> G = nx.Graph([(0, 1), (0, 2), (1, 2)])
>>> H = nx.Graph([(0, 1), (0, 3), (1, 3), (1, 2)])
>>> U = nx.union(G, H, rename=("G", "H"))
>>> U.nodes
NodeView(('G0', 'G1', 'G2', 'H0', 'H1', 'H3', 'H2'))
>>> U.edges
EdgeView([('G0', 'G1'), ('G0', 'G2'), ('G1', 'G2'), ('H0', 'H1'), ('H0', 'H3'), ('H1', 'H3'), ('H1', 'H2')])

Additional backends implement this function

graphblas : OpenMP-enabled sparse linear algebra backend.