insert_endpoint

insert_endpoint(k, target_endpoint, adjacent_endpoint, **attr)

Insert one endpoint into a node’s incidence list (shifting others CCW).

This is a low-level primitive. It does not automatically update the twin at the other node; it simply places the given adjacent endpoint object into the target position.

Parameters:

• k (PlanarDiagram) – Diagram to modify (in place).

• target_endpoint (tuple) – (node, pos) where to place the new endpoint.

• adjacent_endpoint (tuple | Endpoint) – The endpoint object (or tuple convertible to one) to insert into the node’s incidence list at (node, pos).

• **attr – Attributes merged into the endpoint at insertion.

Raises:

ValueError – If target node is not a vertex.

Return type:

None