printer.py

#Simulate a printing task

import random

class Queue:
    def __init__(self):
        self.items = []
    
    def isEmpty(self):
        return self.items == []
    
    def enqueue(self, item):
        self.items.insert(0, item)
        #O(n)

    def dequeue(self):
        return self.items.pop()
        #O(1)

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

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
        #How long seconds it takes to register the task
        #as the next task after the task is created.

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):

        #A new task emerges every second with probability 1/180
        if newPrintTask():
            task = Task(currentSecond)
            printQueue.enqueue(task)

        #In case a new task which already existed in a waiting list
        #will be added to the printer
        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()))

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