import networkx as nx
import matplotlib.pyplot as plt

G = nx.DiGraph()  #creates a 'directed' graph; nx.Graph() creates an undirected graph
G.add_node(1)
G.add_node(2)
G.add_node(3)
G.add_node(4)
G.add_node(5)
G.add_node(6)

G.add_edge(1,2)
G.add_edge(1,3)
G.add_edge(1,5)
G.add_edge(4,5)
G.add_edge(6,5)

print G.nodes(), G.edges()

# Plotting option 1 - using nx.draw_circular()
# Nodes 1 and 5 and the edge running between them are painted with distinct colors.
plt.figure(figsize=(8,8))
nx.draw_circular(G,node_size=500,with_labels=True) #creates a circular graph. Refer http://networkx.lanl.gov/tutorial/tutorial.html#drawing-graphs
nx.draw_circular(G,node_size=500,nodelist=[1,5],edgelist=[(1,5)],node_color='b',edge_color='g',width=3)
plt.axis('equal')
#plt.savefig('circular_graph.png')
plt.show()

# Plotting option 2 - using graphviz_layout()
pos=nx.graphviz_layout(G,prog='circo',args='') #'circo creates circular graph
#for other 'prog' options refer to http://www.graphviz.org/Documentation.php (see 'Layout Commands')
plt.figure(figsize=(8,8))
nx.draw(G,pos,node_size=20,alpha=0.5,node_color="blue", with_labels=False)
plt.axis('equal')
#plt.savefig('circular_graph.png')
plt.show()