python的模拟算法--打印任务

class Queue:
    def __init__(self):
        self.items = []

    def isEmpty(self):
        return self.items == []

    def enqueue(self, item):
        # 队列首段加选项
        self.items.insert(0, item)

    def dequeue(self):
        # 队列尾端出
        return self.items.pop()

    def size(self):
        return len(self.items)

import random

class Printer:
    def __init__(self, ppm):
        self.pagerate = ppm
        self.currentTask = None
        self.timeRemaining = 0

    def tick(self):
        if self.currentTask is not None:
            self.timeRemaining = self.timeRemaining - 1
            if self.timeRemaining <= 0:
                self.currentTask = None

    def busy(self):
        if self.currentTask != None:
            return True
        else:
            return False

    def startNext(self, newtask):
        self.currentTask = newtask
        self.timeRemaining = newtask.getPages() * 60 / self.pagerate


class Task:
    def __init__(self, time):
        self.timestamp = time
        self.pages = random.randrange(1, 21)

    def getStamp(self):
        return self.timestamp

    def getPages(self):
        return self.pages

    def waitTime(self, currenttime):
        return currenttime - self.timestamp


def newPrintTask():
    num = random.randrange(1, 181)
    if num == 180:
        return True
    else:
        return False


def simulation(numSeconds, pagesPerMinute):
    labprinter = Printer(pagesPerMinute)
    printQueue = Queue()
    waitingtimes = []

    for currentSecond in range(numSeconds):
        if newPrintTask():
            task = Task(currentSecond)
            printQueue.enqueue(task)
        if (not labprinter.busy()) and (not printQueue.isEmpty()):
            nexttask = printQueue.dequeue()
            waitingtimes.append(nexttask.waitTime(currentSecond))
            labprinter.startNext(nexttask)
        labprinter.tick()
    averageWait = sum(waitingtimes) / len(waitingtimes)
    print("average wait %6.2f secs %3d task remaining" % (averageWait, printQueue.size()))

for i in range(10):
     simulation(3600,5)