I am using read_dot from pydot (v. 1.4.2-2) and networkx (v. 2.8.8-1ubuntu1), in Python3 (v. 3.12.3).

Sometimes read_dot add an extra vertex with label “n”. I noticed that this has some relation with the presence of a “;” at the end of the last line. For instance, consider the simple code below, in a file named t.

    import sys
    import networkx as nx

    g = nx.Graph(nx.nx_pydot.read_dot(sys.stdin))
    print(g,file=sys.stderr)
    nx.nx_pydot.write_dot(g,sys.stdout)`

Also, consider an input file, name test1.dot.

    graph {
    1 -- 2;
    }

The output of the command
`$ t < test1.dot
gives the output below.

    Graph named 'G' with 3 nodes and 1 edges
    strict graph "G" {
    "n";
    1;
    2;
    1 -- 2;
    }

Note that there is an extra vertex.

If we remove the “;” from the input file, the output is correct.

    Graph named 'G' with 2 nodes and 1 edges
    strict graph "G" {
    1;
    2;
    1 -- 2;
    }

Have someone noticed that error before? Is that a real bug or I am using it in the wrong way?