Solutions - Chapter 4

4-1: Pizzas

Think of at least three kinds of your favorite pizza. Store these pizza names in a list, and then use a for loop to print the name of each pizza.

Modify your for loop to print a sentence using the name of the pizza, instead of printing just the name of the pizza. For each pizza, you should have one line of output containing a simple statement like I like pepperoni pizza.
Add a line at the end of your program, outside the for loop, that states how much you like pizza. The output should consist of three or more lines about the kinds of pizza you like and then an additional sentence, such as I really love pizza!

pizzas.py

favorite_pizzas = ['pepperoni', 'hawaiian', 'veggie']

# Print the names of all the pizzas.
for pizza in favorite_pizzas:
    print(pizza)

print("\n")

# Print a sentence about each pizza.
for pizza in favorite_pizzas:
    print(f"I really love {pizza} pizza!")

print("\nI really love pizza!")

Output:

pepperoni
hawaiian
veggie

I really love pepperoni pizza!
I really love hawaiian pizza!
I really love veggie pizza!

I really love pizza!

4-2: Animals

Think of at least three different animals that have a common characteristic. Store the names of these animals in a list, and then use a for loop to print out the name of each animal. - Modify your program to print a statement about each animal, such as A dog would make a great pet. - Add a line at the end of your program, stating what these animals have in common. You could print a sentence, such as Any of these animals would make a great pet!

animals.py

animals = ["spider monkey", "lemur", "giraffe"]

# Print each animal.
for animal in animals:
    print(animal)

print("\n")

# Print a statement about each animal.
for animal in animals:
    print(f"A {animal} has a long tail.")

print("\nAll of these animals have long tails.")

Output:

spider monkey
lemur
giraffe

A spider monkey has a long tail.
A lemur has a long tail.
A giraffe has a long tail.

All of these animals have long tails.

4-3: Counting to Twenty

Use a for loop to print the numbers from 1 to 20, inclusive.

counting_to_twenty.py

numbers = list(range(1, 21))

for number in numbers:
    print(number)

Output:

4-5: Summing a Million

Make a list of the numbers from one to one million, and then use min() and max() to make sure your list actually starts at one and ends at one million. Also, use the sum() function to see how quickly Python can add a million numbers.

summing_a_million.py

numbers = list(range(1, 1_000_001))

print(min(numbers))
print(max(numbers))
print(sum(numbers))

Output:

1
1000000
500000500000

4-6: Odd Numbers

Use the third argument of the range() function to make a list of the odd numbers from 1 to 20. Use a for loop to print each number.

odd_numbers.py

odd_numbers = list(range(1, 20, 2))

for number in odd_numbers:
    print(number)

Output:

4-7: Threes

Make a list of the multiples of 3 from 3 to 30. Use a for loop to print the numbers in your list.

threes.py

threes = list(range(3, 31, 3))

for number in threes:
    print(number)

Output:

4-8: Cubes

A number raised to the third power is called a cube. For example, the cube of 2 is written as 2**3 in Python. Make a list of the first 10 cubes (that is, the cube of each integer from 1 through 10), and use a for loop to print out the value of each cube.

cubes.py

cubes = []
for number in range(1, 11):
    cube = number**3
    cubes.append(cube)

for cube in cubes:
    print(cube)

Output:

4-9: Cube Comprehension

Use a list comprehension to generate a list of the first 10 cubes.

cube_comprehension.py

cubes = [number**3 for number in range(1,11)]

for cube in cubes:
    print(cube)

Output:

4-11: My Pizzas, Your Pizzas

Start with your program from Exercise 4-1 (page 56). Make a copy of the list of pizzas, and call it friend_pizzas. Then, do the following:

Add a new pizza to the original list.
Add a different pizza to the list friend_pizzas.
Prove that you have two separate lists. Print the message, My favorite pizzas are:, and then use a for loop to print the first list. Print the message, My friend's favorite pizzas are:, and then use a for loop to print the second list. Make sure each new pizza is stored in the appropriate list.

my_pizzas_your_pizzas.py

favorite_pizzas = ['pepperoni', 'hawaiian', 'veggie']
friend_pizzas = favorite_pizzas[:]

favorite_pizzas.append("meat lover's")
friend_pizzas.append('pesto')

print("My favorite pizzas are:")
for pizza in favorite_pizzas:
    print(f"- {pizza}")

print("\nMy friend's favorite pizzas are:")
for pizza in friend_pizzas:
    print(f"- {pizza}")

Output:

My favorite pizzas are:
- pepperoni
- hawaiian
- veggie
- meat lover's

My friend's favorite pizzas are:
- pepperoni
- hawaiian
- veggie
- pesto

4-12: More Loops

All versions of foods.py in this section have avoided using for loops when printing, to save space. Choose a version of foods.py, and write two for loops to print each list of foods.

more_loops.py

my_foods = ['pizza', 'falafel', 'carrot cake']
friend_foods = my_foods[:]

my_foods.append('cannoli')
friend_foods.append('ice cream')

print("My favorite foods are:")
for food in my_foods:
    print(f"- {food}")

print("\nMy friend's favorite foods are:")
for food in friend_foods:
    print(f"- {food}")

Output:

My favorite foods are:
- pizza
- falafel
- carrot cake
- cannoli

My friend's favorite foods are:
- pizza
- falafel
- carrot cake
- ice cream

4-13: Buffet

A buffet-style restaurant offers only five basic foods. Think of five simple foods, and store them in a tuple.

Use a for loop to print each food the restaurant offers.
Try to modify one of the items, and make sure that Python rejects the change.
The restaurant changes its menu, replacing two of the items with different foods. Add a line that rewrites the tuple, and then use a for loop to print each of the items on the revised menu.

buffet.py

menu_items = (
    'rockfish sandwich', 'halibut nuggets', 'smoked salmon chowder',
    'salmon burger', 'crab cakes',
    )

print("You can choose from the following menu items:")
for item in menu_items:
    print(f"- {item}")

menu_items = (
    'rockfish sandwich', 'halibut nuggets', 'smoked salmon chowder',
    'black cod tips', 'king crab legs',
    )

print("\nOur menu has been updated.")
print("You can now choose from the following items:")
for item in menu_items:
    print(f"- {item}")

Output:

You can choose from the following menu items:
- rockfish sandwich
- halibut nuggets
- smoked salmon chowder
- salmon burger
- crab cakes

Our menu has been updated.
You can now choose from the following items:
- rockfish sandwich
- halibut nuggets
- smoked salmon chowder
- black cod tips
- king crab legs