Ford-Fulkerson example for presentation: http://goo.gl/DizfF7

gistfile1.py

from collections import defaultdict

def add(network, a, b, capacity):
	network[a][b] = network[b][a] = capacity

def send(network, a, b, V, minimum=1000000):
    V.add(a)
    if a == b: 
        print '-> path', a
        return minimum

    for node, capacity in network[a].items():
        if node in V or capacity == 0: continue
        sent = send(network, node, b, V, min(minimum, capacity))
        if sent>0:
            print '-> path', a, capacity
            network[a][node] -= sent
            network[node][a] += sent
            return sent

    return 0
            
network = defaultdict(lambda : {})
add(network, 'ford', 'A', 10)
add(network, 'ford', 'B', 100)
add(network, 'A', 'B', 50)
add(network, 'A', 'C', 20)
add(network, 'A', 'D', 10)
add(network, 'B', 'D', 1)
add(network, 'C', 'D', 30)
add(network, 'C', 'E', 100)
add(network, 'D', 'E', 200)
add(network, 'D', 'F', 5)
add(network, 'E', 'F', 100)
add(network, 'E', 'fulkerson', 3)
add(network, 'F', 'fulkerson', 200)

total = 0
while True:
    sent = send(network, 'ford', 'fulkerson', set())
    print 'Sent:', sent
    if not sent: break
    total += sent

print 'Final value:', total