模拟打印任务

class Printer:
    """检查当前是否有待完成的任务"""
    def __init__(self, ppm):
        self.pagerate = ppm
        self.currentTask = None
        self.timeRemaining = 0

    def tick(self):
        if self.currentTask != 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:
    """单个打印任务"""
    def __init__(self, time):
        self.timestamp = time
        self.pages = random.randint(1, 21)

    def getStamp(self):
        return self.timestamp

    def getPages(self):
        return self.pages

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


# 模拟打印任务
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 (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 tasks remaining"
          % (averageWait, printQueue.size()))


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