2015-11-12-134808.sagews

g=graphs.PetersenGraph()

def graph_string(g, w = None):
    """
    Given graph g and (optional) edge weights w return string
    representing g and w in the following format.

    First line is a pair of integers denoting number of vertices
    and number of edges, say m, respectively.

    Then m lines follow, where each line is a pair or a triple of
    numbers. The first two numbers always indicate the endpoints of
    an edge and the third number (if any) indicates the corresponding
    weight of the given edge.

    E.g. If G=(V,E) with V={0, 1, 2, 3} and E={01, 02, 13, 24, 34}, then
    the string representing G is
    4 5
    0 1
    0 2
    1 3
    2 4
    3 4
    """
    g.relabel()
    n = g.num_verts()
    m = g.num_edges()
    s = "{0} {1}\n".format(n, m)
    for x,y in g.edges(labels = False):
        s += "{0} {1}".format(x, y)
        if w:
            s += " {0}".format(w[(x, y)])
        s += "\n"
    return s

def write_to_file( filename, string ):
    f = open(filename,'w')
    f.write(string)
    f.close()

w=dict([(e, randint(1,10)) for e in g.edges(labels = False)])

w

{(0, 1): 7, (1, 2): 2, (6, 9): 10, (4, 9): 5, (6, 8): 9, (5, 7): 1, (2, 7): 8, (1, 6): 8, (3, 8): 2, (0, 5): 9, (0, 4): 5, (2, 3): 1, (3, 4): 4, (5, 8): 3, (7, 9): 1}

s=graph_string(g, w)

write_to_file('test.txt', s)

g=graphs.RandomGNP(250,0.2)
#g.show()
print g.is_connected()

True

︠1b1435c3-ac33-4032-85fd-6cecaafc08cas︠
w=dict([(e, randint(1,1000)) for e in g.edges(labels = False)])
s=graph_string(g,w)
write_to_file("random.txt",s)

g=graphs.Grid2dGraph(40,40)
g.relabel()
for i in range(50):
    u = randint(0,1599)
    v = randint(0,1599)
    g.add_edge(u,v)
g.is_connected()
g.average_degree().n()

True 3.96250000000000

w=dict([(e, randint(1,1000)) for e in g.edges(labels = False)])
s=graph_string(g,w)
write_to_file("gridlike.txt",s)