from __future__ import with_statement 
import threading
import random
import time

terminate = threading.Event()

class Buckets:
    def __init__(self, nbuckets):
        self.nbuckets = nbuckets
        self.values = [random.randrange(10) for i in range(nbuckets)]
        self.lock = threading.Lock()

    def __getitem__(self, i):
        return self.values[i]

    def transfer(self, src, dst, amount):
        with self.lock:
            amount = min(amount, self.values[src])
            self.values[src] -= amount
            self.values[dst] += amount

    def snapshot(self):
        
        with self.lock:
            return self.values[:]

def randomize(buckets):
    nbuckets = buckets.nbuckets
    while not terminate.isSet():
        src = random.randrange(nbuckets)
        dst = random.randrange(nbuckets)
        if dst!=src:
            amount = random.randrange(20)
            buckets.transfer(src, dst, amount)

def equalize(buckets):
    nbuckets = buckets.nbuckets
    while not terminate.isSet():
        src = random.randrange(nbuckets)
        dst = random.randrange(nbuckets)
        if dst!=src:
            amount = (buckets[src] - buckets[dst]) 
            if amount>=0: buckets.transfer(src, dst, amount)
            else: buckets.transfer(dst, src, -amount)

def print_state(buckets):
    snapshot = buckets.snapshot()
    for value in snapshot:
        print '%2d'% value,
    print '=', sum(snapshot)


buckets = Buckets(15)


t1 = threading.Thread(target=randomize, args=[buckets])
t1.start()


t2 = threading.Thread(target=equalize, args=[buckets])
t2.start()


try:
    while True:
        print_state(buckets)
        time.sleep(1)
except KeyboardInterrupt: 
    terminate.set()


t1.join()
t2.join()