Midterm Exam II MCS 275 Programming Tools 14 March 2017

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Victor Dean
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1 NAME: answers The exam is closed book, no notes and no computer. All your answers to the questions below must be submitted on paper. Write your name on this sheet and submit it with your answers. Please do not ask questions during the exam. 1. Consider the function def print_form(): Prints a form to prompt for a PIN number. print( <html> <body> <form action="pinform.py"> <p>give your PIN: <input type="text" name="pin"> <input type="submit"></p> </body> </html>) Define the function to process the form, extending the code below: def processpin(form): Checks whether the form contains a valid 4-digit number. Writes please provide a 4-digit number if the user did enter not a number or if the number is not 4 digits long. Otherwise, writes thanks on the page. 1

2 def print_message(msg): Prints the message in msg. print( <html> <body> %s </body> </html> % msg) def processpin(form): Checks whether the form contains a valid 4-digit number. Writes please provide a 4-digit number if the user did enter not a number or if the number is not 4 digits long. Otherwise, writes thanks on the page. try: data = form[ pin ].value val = int(data) if val >= 1000 and val <= 9999: print_message( thanks ) else: print_message( please provide a 4-digit number ) except: print_message( please provide a 4-digit number ) 2

3 2. Consider the following client/server interaction: (a) The client sends a positive integer number to the server. (b) The server replies by sending to client 0 if the received number is even and 1 if the received number is odd. Write code for the server. from socket import socket as Socket from socket import AF_INET, SOCK_STREAM HOST = PORT = BUFF = 80 ADDR = (HOST, PORT) SERVER = Socket(AF_INET, SOCK_STREAM) SERVER.bind(ADDR) SERVER.listen(1) CLIENT, CLIENTADDR = SERVER.accept() NBR = int(client.recv(buff).decode()) REPLY = len(str(nbr % 2)) CLIENT.send(str(REPLY).encode()) CLIENT.close() SERVER.close() 3

4 3. A clothing store maintains a database Goods with a table items: mysql> explain items; Field Type Null Key Default Extra idn int(11) YES NULL desciption char(80) YES NULL price float YES NULL The data to fill up the table items is on file, a comma separated file with name clothing.txt. Every line on file has the format idn, description, price where idn is an integer, description a string of 80 characters or less, and price is a float. Write a Python script to read the file clothing.txt and to fill up the table items of the database Goods. import pymysql OURDB = pymysql.connect(db= Goods ) CRS = OURDB.cursor() FILE = open( clothing.txt, r ) while True: LINE = FILE.readline() if LINE == : break DATA = LINE.split(, ) idn = int(data[0]) des = DATA[1] prc = float(data[2]) CMD = insert into items values ( %d, % idn \ + \"%s\", % des \ + %.2f) % prc CRS.execute(CMD) FILE.close() OURDB.commit() OURDB.close() 4

5 4. Consider a list jobs of positive integer numbers. Each number in the list represents the time to complete a job. The processing of jobs[k] is simulated by sleep(jobs[k]). A crew of T threads will process the jobs. Thread t does job k if k % T == t. The name of each thread is the string representation of the thread number: thread t has name str(t). The constructor is defined below. Write code for the the run method. from threading import Thread from time import sleep class Worker(Thread): Simulates a work crew. def init (self, name, jobs, nbrt): Defines the thread with given name to process a list of jobs. The number of threads is in nbrt. Thread. init (self, name=name) self.jobs = jobs self.nbrt = nbrt Provide a good documentation string of your definition of the run method. def run(self): If the remainder after division by nbrt of the job with index k equals i, then thread i sleeps as longs as jobs[k]. name = self.getname() idx = int(name) print( hello from thread, name) for k in range(len(self.jobs)): if k % self.nbrt == idx: print( thread, idx, sleeps, self.jobs[k]) sleep(self.jobs[k]) 5

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