The name/ family name of the (di)graph is preserved on addition/ deletion of a vertex/ an edge.

[janmenjayap]

Steps To Reproduce

Consider the following example:
Upon deleting a vertex from the Petersen graph, the string representation of the resulting graph still states that the new graph is the Petersen graph.

sage: P = graphs.PetersenGraph()
sage: P
Petersen graph: Graph on 10 vertices
sage: P.delete_vertex(0)
sage: P
Petersen graph: Graph on 9 vertices

Upon deleting an edge from a cycle graph, the string representation of the resulting graph still states that the new graph is a cycle graph:

sage: G = graphs.CycleGraph(4)
sage: G
Cycle graph: Graph on 4 vertices
sage: G.delete_edge(0, 1)
sage: G
Cycle graph: Graph on 4 vertices

An analogous result can be observed for each instance of a named (di)graph/ (di)graph of a particular family. An example for digraph goes as follows:

sage: D = digraphs.Circuit(5)
sage: D
Circuit: Digraph on 5 vertices
sage: D.delete_edge(0, 1)
sage: D
Circuit: Digraph on 5 vertices

Analogous behaviour may be observed in case of addition of a vertex/ an edge:

sage: G = graphs.CycleGraph(4)
sage: G
Cycle graph: Graph on 4 vertices
sage: G.add_vertex()
4
sage: G
Cycle graph: Graph on 5 vertices

Expected Behavior

A (possible) expected behaviour can be to remove the prefix substring pertaining to the family name/ name of the (di)graph on the addition/ deletion of a vertex/ an edge. The expected behaviour for the above mentioned examples are listed below:

sage: P = graphs.PetersenGraph()
sage: P
Petersen graph: Graph on 10 vertices
sage: P.delete_vertex(0)
sage: P
Graph on 9 vertices

sage: G = graphs.CycleGraph(4)
sage: G
Cycle graph: Graph on 4 vertices
sage: G.delete_edge(0, 1)
sage: G
Graph on 4 vertices

sage: D = digraphs.Circuit(5)
sage: D
Circuit: Digraph on 5 vertices
sage: D.delete_edge(0, 1)
sage: D
Digraph on 5 vertices

sage: G = graphs.CycleGraph(4)
sage: G
Cycle graph: Graph on 4 vertices
sage: G.add_vertex()
4
sage: G
Graph on 5 vertices

Actual Behavior

The name/ family name of the (di)graph is preserved on addition/ deletion of a vertex/ an edge. For examples see the section: Steps to reproduce

Additional Information

This problem may be solved by setting self.name() or the output of self.str() to '' on the addition/ deletion of a vertex/ an edge.

This issue shall also be corrected for the addition of cliques, cycles, paths and removable of multiedges.

Environment

• OS: Ubuntu 20.04.6 LTS (Focal Fossa)
• Sage Version: 10.5.beta6

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide