Question

我正在修读数据结构课程，而我不了解课程如何调用另一个课程中的方法。
以下代码有两个类：Printer和Task 请注意，类Printer有一个名为startNext的方法，其变量self.timeRemaining会被赋予newTask.getPages() * 60/self.pagerate的结果。

newTaks如何从Task类引用getPages()方法？
将此对象传递给Printer类的代码从不引用Task类代码有效，因为这是课程提供的内容，但我无法理解如何访问该方法代码：

from pythonds.basic.queue import Queue

import random

class Printer:

    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:

    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 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 tasks remaining." % (averageWait, printQueue.size())

def newPrintTask():
    num = random.randrange(1, 181)

    if num == 180:
        return True
    else:
        return False

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

Answer 1

如果我清楚地理解你的问题，那是因为你要将任务对象添加到队列列表中。然后，当您获得对象（列表项）时，您将再次获得任务对象：

#creating Task object and adding to Queque list
task = Task(currentSecond)
printQueue.enqueue(task)

class Queue:
    def __init__(self):
        #list of task objects
        self.items = []

    def enqueue(self, item):
        #you are inserting Task object item to list
        self.items.insert(0,item)

    def dequeue(self):
       #returns task object
       return self.items.pop()

那么你可以从Printer类调用startNext（）方法，因为dequeue（）方法正在返回Task对象。

由于startNext（）中的对象是Task的类型，您可以在该对象上调用getPages（）方法。

答案是否足够？

类和外部方法调用

1 个答案: