is_loop

is_loop(k, arc_or_endpoint)

Return True if an arc/endpoint forms a loop (an arc whose ends are on the same node which is a Vertex).

Parameters:

• k (PlanarDiagram) – Diagram.

• arc_or_endpoint – Either a single Endpoint or a 2-endpoint container (arc).

Return type:

bool

Notes

“Kink” is a special loop notion at crossings; see is_kink.