This documents an unmaintained version of NetworkX. Please upgrade to a maintained version and see the current NetworkX documentation.


node_boundary(G, nbunch1, nbunch2=None)[source]

Returns the node boundary of nbunch1.

The node boundary of a set S with respect to a set T is the set of nodes v in T such that for some u in S, there is an edge joining u to v. If T is not specified, it is assumed to be the set of all nodes not in S.

  • G (NetworkX graph)
  • nbunch1 (iterable) – Iterable of nodes in the graph representing the set of nodes whose node boundary will be returned. (This is the set S from the definition above.)
  • nbunch2 (iterable) – Iterable of nodes representing the target (or “exterior”) set of nodes. (This is the set T from the definition above.) If not specified, this is assumed to be the set of all nodes in G not in nbunch1.

The node boundary of nbunch1 with respect to nbunch2.

Return type:



Any element of nbunch that is not in the graph G will be ignored.

nbunch1 and nbunch2 are usually meant to be disjoint, but in the interest of speed and generality, that is not required here.