Niche model of food webs in python

nichemodel.py

def niche_foodweb(S, C):
    G = nx.DiGraph()
    G.add_nodes_from([n for n in xrange(S)])
    ## Step 1 - create random species
    for n in G:
        G.node[n]['n'] = np.round(np.random.uniform(),2)
        G.node[n]['r'] = np.random.beta(1, 1/float(2*C)-1) * G.node[n]['n']
        G.node[n]['c'] = np.random.uniform(G.node[n]['r']/float(2),G.node[n]['n'])
    ## Step 2 - smallest species are basal
    Smallest = np.min([G.node[n]['n'] for n in G])
    for n in G:
        if G.node[n]['n'] == Smallest:
            G.node[n]['r'] = 0
    ## Step 3 - create the links
    for n1 in G:
        for n2 in G:
            if G.node[n2]['n'] <= G.node[n1]['c']+G.node[n1]['r']:
                if G.node[n2]['n'] >= G.node[n1]['c']-G.node[n1]['r']:
                    G.add_edge(n1, n2)
    return G