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Python for everybody Week 7 Quiz Answer

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Python Data Structures

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Python Data Structures Week 7 Quiz Answers

 
Question 1)
Given the architecture and terminology we introduced in Chapter 1, where are files stored?
  • Motherboard
  • Central Processor
  • Machine Language
  • Secondary memory
 
Question 2)
What is stored in a “file handle” that is returned from a successful open() call?
  • The handle is a connection to the file’s data
  • The handle contains the first 10 lines of a file
  • The handle has a list of all of the files in a particular folder on the hard drive
  • All the data from the file is read into memory and stored in the handle
 
Question 3)
What do we use the second parameter of the open() call to indicate?
  • What disk drive the file is stored on
  • How large we expect the file to be
  • The list of folders to be searched to find the file we want to open
  • Whether we want to read data from the file or write data to the file
 
Question 4)
What Python function would you use if you wanted to prompt the user for a file name to open?
  • input()
  • cin
  • file_input()
  • read()
 
Question 5)
What is the purpose of the newline character in text files?
  • It enables random movement throughout the file
  • It adds a new network connection to retrieve files from the network
  • It indicates the end of one line of text and the beginning of another line of text
  • It allows us to open more than one files and read them in a synchronized manner
 
Question 6)
If we open a file as follows:
 
xfile = open(‘mbox.txt’)
 
What statement would we use to read the file one line at a time?</span ></b >
  • for line in xfile:
  • while ( getline (xfile,line) ) {
  • READ xfile INTO LINE
  • READ (xfile,*,END=10) line
 
Question 7)
What is the purpose of the following Python code?</span ></b >
fhand = open(‘mbox.txt’)
x = 0
for line in fhand:
        x = x + 1
print x
  • Count the lines in the file ‘mbox.txt’
  • Reverse the order of the lines in mbox.txt
  • Convert the lines in mbox.txt to upper case
  • Remove the leading and trailing spaces from each line in mbox.txt
 
Question 8)
If you write a Python program to read a text file and you see extra blank lines in the output that are not present in the file input as shown below, what Python string function will likely solve the problem?</span ></b >
 
From: stephen.marquard@uct.ac.za
From: louis@media.berkeley.edu
From: zqian@umich.edu
From: rjlowe@iupui.edu
  • find()
  • rstrip()
  • split()
  • startswith()
 
Question 9)
The following code sequence fails with a traceback when the user enters a file that does not exist. How would you avoid the traceback and make it so you could print out your own error message when a bad file name was entered?

</span >
fname = raw_input(‘Enter the file name: ‘)
fhand = open(fname)
  • try / except
  • signal handlers
  • try / catch / finally
  • on error resume next
 
Question 10)
What does the following Python code do?
 
fhand = open(‘mbox-short.txt’)
inp = fhand.read()
 
  • Checks to see if the file exists and can be written
  • Turns the text in the file into a graphic image like a PNG or JPG
  • Reads the entire file into the variable inp as a string
 

Week 7 Assignment 1

7.1 Write a program that prompts for a file name, then opens that file and reads through the file, and print the contents of the file in upper case. Use the file words.txt to produce the output below.
You can download the sample data at http://www.pythonlearn.com/code/words.txt
# Use words.txt as the file name
fname = raw_input(“Enter file name: “)
fh = open(fname)
 
for line in fh:
        line = line.rstrip()
line = line.upper()
print line

Week 7 Assignment 2

7.2 Write a program that prompts for a file name, then opens that file and reads through the file, looking for lines of the form: X-DSPAM-Confidence:    0.8475
Count these lines and extract the floating point values from each of the lines and compute the average of those values and produce an output as shown below.
You can download the sample data at http://www.pythonlearn.com/code/mbox-short.txt when you are testing below enter mbox-short.txt as the file name.
# Use the file name mbox-short.txt as the file name
fname = input(“Enter file name: “)
fh = open(fname)
sum = 0.0
count = 0
 
for line in fh:
        if not line.startswith(“X-DSPAM-Confidence:”) :
                continue
        else:
                sum = sum + float(line[20:])
                count = count + 1
 
print(“Average spam confidence:”, sum/count)