Python/Sage code for generating random weighted graphs

random_weighted_graph.py

'''
Generates a random weighted graph in Sage. 
n = Number of nodes. 
p = Probability of two nodes being connected. Must be between 0 and 1. 
Weights on the edges are randomly generated integers situated between lower_weight and upper_weight. 
Example: random_weighted_graph(6, 0.25, 10, 20) creates a weighted graph with 6 nodes, a 1/4 probability 
of two nodes being connected, and weights on the edges randomly selected between 10 and 20. 
'''

def random_weighted_graph(n, p, lower_weight, upper_weight): 
    import random
    g = graphs.RandomGNP(n,p)
    m = g.num_edges()
    weights = [random.randint(lower_weight, upper_weight) for r in xrange(m)]
    uw_edges = g.edges()
    
    # Create weighted graph edge list 
    w_edges = [(uw_edges[i][0], uw_edges[i][1], weights[i]) for i in xrange(m)]
    
    return Graph(w_edges, weighted = True)

Hi
I used of this code in my project bud in 12 line 'g = graphs.RandomGNP(n,p)' I see an error : name 'RandomGNP' is not defined. Can you help me?