philosophers.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
5 philosophers at a round table w/ bowls of spaghetto

Forks are placed between each pair of philosophers (5 forks)

Must think and eat

Can only eat when he has both left and right forks

Each fork can only be held by 2 philosopher at a time

so they can only use it if not being used by another

After eating he must put down both forks and they become available to
others.

Ph can take one or the other, but cannot start eating until getting both
forks.

   . o . o
  o       .
   . o . o
"""

class Philosopher(object):
    def __init__(self, name, **kw):
        self.name = name
        self.eating = False
        self.num_times = 0
        for k, v in kw:
            setattr(self, k, v)

    def __repr__(self):
        return 'Philosopher("%s", eating=%s, num_times=%s)' % (self.name, self.eating, self.num_times)

    def step(self, left, right):
        #print 'name=%s left(%s).eating=%s right(%s).eating=%s' % (self.name, left.name, left.eating, right.name, right.eating)
        if self.eating:
            self.eating = False
        elif not left.eating and not right.eating:
            self.eating = True
            self.num_times += 1

class System(object):
    def __init__(self):
        self.philosophers = [
            Philosopher('A'),
            Philosopher('B'),
            Philosopher('C'),
            Philosopher('D'),
            Philosopher('E'),
        ]

    def __repr__(self):
        out = ''
        for i in range(0, len(self.philosophers)):
            out += '    %s\n' % (self.philosophers[i],)
        return out.rstrip()

    def step(self):
        for i in range(0, len(self.philosophers)):
            right_index = i + 1
            if right_index >= len(self.philosophers):
                right_index = 0
                #print 'i=%s rindex=-1 %s' % (i, self.philosophers[right_index].name)
            self.philosophers[i].step(self.philosophers[i-1], self.philosophers[right_index])

def main():
    system = System()
    print 'Initial table configuration:\n%s' % (system,)
    for i in range(1, 6):
        system.step()
        print 'i=%s Table configuration:\n%s' % (i, system,)

if __name__ == '__main__':
    main()