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The output of a command like graphs.planar_graphs(4) is an iterator that can yield all planar graphs with the specified number of vertices.

To get the documentation, do one of the following:

• in Sage, type graphs.planar_graph? and hit the return or enter key.

  This will display the documentation for this function, in text mode.

• in Sage, type graphs.planar_graph?? and hit the return or enter key.

  This will display the code source for this function, including the documentation string.

• in Sage, type browse_sage_doc(graphs.planar_graph).

  This will open the documentation for this function, in html, in a browser tab.

• browse the online documentation:

  • SageMath documentation for planar_graphs

So for example, if you define

sage: gen = graphs.planar_graphs(n)

and turn it into a list

sage: G = list(gen)

you could display a summary of this list of graphs and their diameters:

sage: newline = '\n'
sage: s = 'There are {} planar graphs on {} vertices.'
sage: s = s.format(n, len(G))
sage: for j, g in enumerate(G):
....:     s += newline + '{}.'.format(j)
....:     s += newline + 'Edges: {}'.format(g.edges(labels=False))
....:     s += newline + 'Diameter: {}'.format(g.diameter())
....:
sage: print(s)
There are 4 planar graphs on 6 vertices.
0.
Edges: [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
Diameter: 1
1.
Edges: [(1, 2), (1, 3), (2, 3), (2, 4), (3, 4)]
Diameter: 2
2.
Edges: [(1, 2), (1, 3), (2, 4), (3, 4)]
Diameter: 2
3.
Edges: [(1, 2), (2, 3), (2, 4), (3, 4)]
Diameter: 2
4.
Edges: [(1, 2), (2, 3), (3, 4)]
Diameter: 3
5.
Edges: [(1, 2), (2, 3), (2, 4)]
Diameter: 2

or plot them all:

sage: for g in G:
....:     plot(g)
....: 
Launched png viewer for Graphics object consisting of 11 graphics primitives
Launched png viewer for Graphics object consisting of 10 graphics primitives
Launched png viewer for Graphics object consisting of 9 graphics primitives
Launched png viewer for Graphics object consisting of 9 graphics primitives
Launched png viewer for Graphics object consisting of 8 graphics primitives
Launched png viewer for Graphics object consisting of 8 graphics primitives

etc.

Don't hesitate to suggest any specific improvement to the documentation.