Chapter 7

Question 1

numbers = [1, 2, 3, 4, 5]
numbers[2] = 99
print(numbers)

Answer 1

[1, 2, 99, 4, 5]

Question 2

numbers = list(range(3))
print(numbers)

Answer 2

[0, 1, 2]

Question 3

numbers = [10] * 5
print(numbers)

Answer 3

[10, 10, 10, 10, 10]

Question 4

numbers = list(range(1, 10, 2))
for n in numbers:
print(n)

Answer 4

1
3
5
7
9

Question 5

numbers = [1, 2, 3, 4, 5]
print(numbers[−2])

Answer 5

4

Question 6

How do you find the number of elements in a list?

Answer 6

Use the build-in len function

Question 7

numbers1 = [1, 2, 3]
numbers2 = [10, 20, 30]
numbers3 = numbers1 + numbers2
print(numbers1)
print(numbers2)
print(numbers3)

Answer 7

[1, 2, 3]
[10, 20, 30]
[1, 2, 3, 10, 20, 30]

Question 8

numbers1 = [1, 2, 3]
numbers2 = [10, 20, 30]
numbers2 += numbers1
print(numbers1)
print(numbers2)

Answer 8

[1, 2, 3]
[10, 20, 30, 1, 2, 3]

Question 9

numbers = [1, 2, 3, 4, 5]
my_list = numbers[1:3]
print(my_list)

Answer 9

[2, 3]

Question 10

numbers = [1, 2, 3, 4, 5]
my_list = numbers[1:]
print(my_list)

Answer 10

[2, 3, 4, 5] ? [2, 3]

Question 11

numbers = [1, 2, 3, 4, 5]
my_list = numbers[:1]
print(my_list)

Answer 11

[1]

Question 12

numbers = [1, 2, 3, 4, 5]
my_list = numbers[:]
print(my_list)

Answer 12

[1, 2, 3, 4, 5]

Question 13

numbers = [1, 2, 3, 4, 5]
my_list = numbers[−3:]
print(my_list)

Answer 13

[3, 4, 5]

Question 14

names = [‘Jim’, ‘Jill’, ‘John’, ‘Jasmine’]
if ‘Jasmine’ not in names:
print(‘Cannot find Jasmine.’)
else:
print(“Jasmine’s family:”)
print(names)

Answer 14

Jasmine’s family:
[‘Jim’, ‘Jill’, ‘John’, ‘Jasmine’]

Question 15

What is the difference between calling a list’s remove method and using the del statement to remove an element?

Answer 15

The remove method searches for and removes an element containing a specific value.

The del statement removes an element at a specific index.

Question 16

How do you find the lowest and highest values in a list?

Answer 16

You can use the built-in min and max functions.

Question 17

How do you find the lowest and highest values in a list?

names = []

Which of the following statements would you use to add the string ‘Wendy’ to the list at index 0? Why would you select this statement instead of the other?

a. names[0] = ‘Wendy’
b. names.append(‘Wendy’)

Answer 17

You would use statement b, names.append(‘Wendy’).

This is because element 0 does not exist.

If you try to use statement a, an error will occur.

Question 18

Describe the following list methods:

a. index
b. insert
c. sort
d. reverse

Answer 18

• Index method searches for an item in the list and returns the index of the first element containing that item.
• Insert method inserts an item into the list at a specified index.
• Sort method sorts the items in the list to appear in ascending order.
• Reverse method reverses the order of the items in the list.

Question 19

Look at the following list comprehension:

[x for x in my_list]

What is the result expression? What is the iteration expression?

Answer 19

The result expression is: x

The iteration expression is: for x in my_list

Question 20

After this code executes, what value will the list2 list hold

list1 = [1, 12, 2, 20, 3, 15, 4]
list2 = [n*2 for n in list1]

Answer 20

[2, 24, 4, 40, 6, 30, 8]

Question 21

After this code executes, what value will the list2 list hold?

list1 = [1, 12, 2, 20, 3, 15, 4]
list2 = [n for n in list1 if n > 10]

Answer 21

[12, 20, 15]

Question 22

Look at the following interactive session, in which a two-dimensional list is created. How many rows and how many columns are in the list?

numbers = [[1, 2], [10, 20], [100, 200], [1000, 2000]]

Answer 22

The list contains 4 rows and 2 columns.

Question 23

Write a statement that creates a two-dimensional list with three rows and four columns. Each element should be assigned the value 0.

Answer 23

mylist = [[0, 0, 0, 0], [0, 0, 0, 0],
[0, 0, 0, 0]]

Question 24

Write a set of nested loops that display the contents of the numbers list shown in Checkpoint question 7.22.

Answer 24

for r in range(4):
for c in range(2):
print(numbers[r][c])

Question 25

What is the primary difference between a list and a tuple?

Answer 25

The primary difference between tuples and lists is that tuples are immutable. That means that once a tuple is created, it cannot be changed.

Question 26

Give two reasons why tuples exist.

Answer 26

Processing a tuple is faster than processing a list

Tuples are safe. Because you are not allowed to change the contents of a tuple

Question 27

Assume my_list references a list. Write a statement that converts it to a tuple.

Answer 27

my_tuple = tuple(my_list)

Question 28

Assume my_tuple references a tuple. Write a statement that converts it to a list.

Answer 28

my_list = list(my_tuple)

Question 29

This term refers to an individual item in a list.

Answer 29

element -

bin

cubbyhole

slot

Question 30

This is a number that identifies an item in a list.

Answer 30

index

Question 31

This is the first index in a list.

Answer 31

0

Question 32

This is the last index in a list.

Answer 32

The size of the list minus one

Question 33

This will happen if you try to use an index that is out of range for a list.

Answer 33

An IndexError exception will occur.

Question 34

This function returns the length of a list.

Answer 34

len

Question 35

When the * operator’s left operand is a list and its right operand is an integer, the operator becomes this.

Answer 35

The repetition operator

Question 36

This list method adds an item to the end of an existing list.

Answer 36

append

Question 37

This removes an item at a specific index in a list.

Answer 37

the del statement

Question 38

Assume the following statement appears in a program:

mylist = []

Which of the following statements would you use to add the string ‘Labrador’ to the list at index 0?

mylist[0] = ‘Labrador’

mylist.insert(0, ‘Labrador’)

mylist.append(‘Labrador’)

mylist.insert(‘Labrador’, 0)

Answer 38

mylist.insert(0, ‘Labrador’)

Question 39

If you call the index method to locate an item in a list and the item is not found, this happens.

Answer 39

A ValueError exception is raised.

Question 40

This built-in function returns the highest value in a list.

Answer 40

max

Question 41

This function in the random module returns a random element from a list.

Answer 41

choice

random_element = random.choice(my_list)

Question 42

This function in the random module returns multiple, nonduplicated random elements from a list.

Answer 42

sample

random_elements = random.sample(my_list, 3)

Question 43

This file object method returns a list containing the file’s contents.

Answer 43

readlines

with open(‘example.txt’, ‘r’) as file:
file_contents = file.readlines()
print(file_contents)

Question 44

Which of the following statements creates a tuple?

Answer 44

values = (1,)

In Python, tuples are defined using parentheses. The comma after the single element 1 distinguishes it as a tuple. A single element within parentheses without the comma would be interpreted as an expression in parentheses rather than a tuple.