How to get a graph back from canonical_label graph6_string

edit

You could define the following function.

def get_graphs_from_file(filename):
    f = open( filename, 'r')
    graph_list=[ Graph( l[:-1] ) for l in f ]
    f.close()
    return graph_list

And now, assuming the file graphs.g6 contains a graph6 string per line, just run

sage: L=get_graphs_from_file( 'graphs.g6')

That should leave you with a list L of graphs.