Revision history [back]

To get the documentation on the function you mention, you do:

sage: graphs.planar_graphs?

which gives:

[...]

   An iterator over connected planar graphs using the plantri
   generator.

   This uses the plantri generator (see [plantri]) which is available
   through the optional package plantri.

   Note: The non-3-connected graphs will be returned several times,
     with all its possible embeddings.

[...]

You may also read the documentation of planar_graphs function online.

The output is not a graph, neither a list. It is an iterator of graphs.