edge_boundary

edge_boundary(G, nbunch1, nbunch2=None, data=False, keys=False, default=None)

Returns the edge boundary of nbunch1.

The edge boundary of a set S with respect to a set T is the set of edges (u, v) such that u is in S and v is in T. If T is not specified, it is assumed to be the set of all nodes not in S.

Parameters:

GNetworkX graph

nbunch1iterable

Iterable of nodes in the graph representing the set of nodes whose edge boundary will be returned. (This is the set S from the definition above.)

nbunch2iterable

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.

keysbool

This parameter has the same meaning as in MultiGraph.edges().

databool or object

This parameter has the same meaning as in MultiGraph.edges().

defaultobject

This parameter has the same meaning as in MultiGraph.edges().

Returns:

iterator

An iterator over the edges in the boundary of nbunch1 with respect to nbunch2. If keys, data, or default are specified and G is a multigraph, then edges are returned with keys and/or data, as in MultiGraph.edges().

Notes

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.

Examples

>>> G = nx.wheel_graph(6)

When nbunch2=None:

>>> list(nx.edge_boundary(G, (1, 3)))
[(1, 0), (1, 2), (1, 5), (3, 0), (3, 2), (3, 4)]

When nbunch2 is given:

>>> list(nx.edge_boundary(G, (1, 3), (2, 0)))
[(1, 0), (1, 2), (3, 0), (3, 2)]