Chapter 14: Files

Question 1

Define a Transient progam.

Answer 1

A program that runs for a set period and when it stops, the data disappears.
Running the program again, starts with a clean slate.

Question 2

Define a Persistent program.

Answer 2

A program that runs for a long time (or all the time); keep at least some of their data in permanent storage; if they shut down and restart, they pick up where they left off.
Example of persistent program: Windows 10

Question 3

” “ returns a file object that provides methods for working with the file.

Answer 3

open

Question 4

The “” method puts data into the file.

Answer 4

write

Question 5

You’ve used “open” to read the file, what do you need to do when you are done with the file?

Answer 5

close it. variable.close()
Note: If you don’t close the file, it gets closed for you when the program ends.

Question 6

The argument of write has to be a?

Answer 6

string
variable.write(str(53))

Question 7

What does ‘%d’ do?

Answer 7

Formats an integer to a string.

Question 8

What does ‘%g’ do?

Answer 8

Formats to a floating point

Question 9

What does ‘%s’ do?

Answer 9

Formats a string

Question 10

Files are organized into?

Answer 10

directories

Question 11

The “” module provides functions for working with files and directories.

Answer 11

os (stands for operating system)

Question 12

A string like ‘/home/dinsdale’ that identifies a file or directory is called a “”

Answer 12

path

Question 13

A simple filename, like memo.txt is also considered a path, but it is a “” path because it relates to the current directory.

Answer 13

relative

Question 14

A path that begins with / does not depend on the current directory; it is called an “” path.

Answer 14

absolute
»> os.path.abspath(‘memo.txt’)
‘/home/dinsdale/memo.txt’

Question 15

os.path.”” checks whether an item is a file.

Answer 15

isfile
os.path.isfile

Question 16

What does os.listdir do?

Answer 16

list the files in a given directory.
os.listdir(cwd)
[‘music’, ‘photos’, ‘memo.txt’]

Question 17

os.path.”” takes a directory and a file name and joins them into a complete path.

Answer 17

.join

Question 18

Handling an exception with a try statement is called?

Answer 18

catching an exception

Question 19

A “ “ is a sequence of instructions that specifies how to perform a computation.

Answer 19

program

Question 20

” “ returns a file object that provides methods for working with the file.

Answer 20

open

Question 21

What will the output of the following program be?
try:
fin = open(‘answer.txt)
fin.write(‘Yes’)
except:
print(‘No’)
print(‘Maybe’)

Answer 21

No
Maybe

Question 22

What is the output from the following interactive Python statement?

> > > ‘%g’ % (0.1)

Answer 22

0.1
%g is for floating points. If you were to put a %d instead, you would get 0.

Question 23

import os
cwd = os.getcwd()

Which answer is most likely output from the following Python statement?

os.listdir(cwd)

Answer 23

[‘Music’, ‘Pictures’, ‘Desktop’, ‘Library’, ‘Documents’, ‘Downloads’]

Question 24

Consider the following Python program.

fin = open(‘words.txt’)
for line in fin:
word = line.strip()
print(word)

What is word?

Answer 24

A string with no newline

Question 25

Exceptions allow the programmer to _________________.

Answer 25

Write code to handle runtime errors

Question 26

Assume the following Python code has already executed. import os cwd = os.getcwd() Which answer is most likely output from the following Python statement? os.path.exists(cwd)

Answer 26

True

Question 27

Assume the following Python code has already executed. import os cwd = os.getcwd() Which answer is most likely output from the following Python statement? os.path.isdir(cwd)

Answer 27

True

Question 28

Which of the following Python statements runs without error? a. open('three.txt').write(3) b. open('three.txt','w').write(3) c. open('three.txt','w').write(str(3))

Answer 28

c. The write method needs a string in order to work.

Question 29

import os cwd = os.getcwd() Which answer is most likely output from the following Python statement? os.path.join(cwd, 'Documents/file.txt')

Answer 29

/Users/me/Documents/file.txt

Question 30

Will the following program work? fout = open('text.txt, 'w') line1 = "This is line 1" line2 = 'This is line 2' fout.write(line1, line2)

Answer 30

No. write only takes one argument. You can, however, concatenate the two variables. fout.write(line1 + line2) This is legal.

Question 31

When you are done with a file you should "" the file.

Answer 31

close variable.close()

Question 32

What will the output be for the following print statement? print("format is the number %d method for %s when using floats like %g" % (1,"nerds", 9.9))

Answer 32

format is the number 1 method for nerds when using floats like 9.9

Question 33

What does the following do? os.path.exists('example.txt')

Answer 33

Checks whether a file or directory exists. >>> os.path.exists('example.txt') True

Question 34

What does the following do? os.path.isdir('example.txt')

Answer 34

Checks if it's a directory >>> os.path.isdir('example.txt') False >>> os.path.isdir('/home/dinsdale') True