epidemic.py

from collections import defaultdict

def epidemic(self, packet, state):
    '''
    Routes a packet if it hasn't sent the packet on a link yet.
    Always returns False.
    '''
    if 'sent' not in state:
        state['sent'] = defaultdict(dict)
    sent = state['sent']

    for met in self.links:
        if packet not in sent[met]:
            sent[met][packet] = True
            self.send(met, packet)
    return False