Question

Problem 1 Recall that when the built-in function open() is called to open a file for reading, but it doesn't exist, an exception is raised. However, if the file exists, a reference to the opened file object is returned. Write a function safeOpen() that takes one parameter, filename - a string giving the pathname of the file to be opened for reading. When safeOpen() is used to open a file, a reference to the opened file object should be returned if no exception is raised, just like for the open() function. If an exception is raised while trying to open the file, safeOpen() should return the value None. For example, assuming the file ghost.txt doesn't exist, the following is correct output: >>> # open() >>> print (open('ghost.txt')) Traceback (most recent call last): File "<pyshell#8>", line 1, in <module> print(open('ghost.txt')) FileNotFoundError: [Errno 2] No such file or directory: 'ghost.txt >>> • safeOpen() >>> inputFile = safeOpen('ghost.txt') >>> print(inputFile) None >>>

Answer 1

def safeOpen(filename):

   try:
       file = open(filename)
   except:
       file = None

   return file

def safeFloat(x):

   try:
       float(x)
       return True

   except ValueError:
       return False

def averageSpeed():

   filename = input("Enter file name: ")
   file = safeOpen(filename)
   if file == None:
       print("File not found. Please try again")

       filename = input("Enter file name: ")
       file = safeOpen(filename)
       if file == None:
           print("File not found. Yet another human error. Goodbye")
           return None

   content = file.readlines()
   avg_speed = []
   for i in content:
       a = i.split()
       for j in a:
           if safeFloat(j) and float(j) > 2.0:
               avg_speed.append(float(j))

   print("Average speed is " + str(round(sum(avg_speed)/len(avg_speed),2)) + " miles per hour")

averageSpeed()