Chapter 6: Dictionaries

Question 1

create a simple dictionary and call a value

Answer 1

alien_0 = {‘color’: ‘green’, ‘points’: 5}
print(alien_0[‘color’])
print(alien_0[‘points’])

Question 2

what are key-value pairs

Answer 2

a set of values associated with each other

each key is connected to a value, and you can use a key to access the value associated with that key

Question 3

access a value from a dictionary by putting it into a variable and then printing an f-string

Answer 3

new_points = alien_0[‘points’]

print(f”You just earned {new_points} points”)

Question 4

add new key-value pairs

Answer 4

alien_0['x_position'] = 0
alien_0['y_position'] = 25

Question 5

start with an empty dictionary and fill it

Answer 5

alien_0 = {}

alien_0['color'] = 'green'
alien_0['points'] = 5

Question 6

modify the values in the dictionary

Answer 6

alien_0[‘color’] = ‘yellow’

print(f” The alien is now {alien_0[‘color’]}”)

Question 7

Track the position of an alien that moves at different speeds. Store a value representing the alien’s current speed and then use it to determine how far to the right the aliens should move.

Answer 7

#move the alien to the right
#determine how far to move the alien based on its current speed
if alien_0['speed'] =='slow':
    x_increment = 1
elif alien_0['speed'] == 'medium':
     x_increment = 2
else:
#this must be a fast alien
    x_increment = 3

#the new position is the old position plus the increment.
alien_0['x_position'] = alien_0['x_position'] + x_increment

print(f”New position: {alien_0[‘x_position’]}”)

Question 8

use the del statement to completely remove a key-value pair

Answer 8

alien_0 = {‘color’: ‘green’, ‘points’: 5}

del alien_0[‘points’]

Question 9

make a dictionary of people with similar values, and then writhe a variable used in an f-string that states something about one of the people’s values from the dictionary

Answer 9

favorite_languages = {
    'jen': 'python',
    'sarah': 'c',
    'edward': 'ruby',
    'phil': 'python',
    }

language = favorite_languages[‘sarah’].title()
print(f”Sarah’s favorite language is {language}”)

Question 10

what does .get()

Answer 10

sets a default value that will be returned if a requested key doesn’t exist

Question 11

create a dictionary and use .get() to set a default value if a key doesn’t exist

Answer 11

alien_0 = {‘color’: ‘green’, ‘speed’: ‘slow’}
point_value = alien_0.get(‘points’, ‘No point value assigned.’)
print(point_value)

Question 12

store a person’s username, first name, and last name in a dictionary

then write a for loop to access it with the use of two f-strings separating what the key and value are

Answer 12

user_0 = {
    'username': 'efermi',
    'first': 'enrico',
    'last': 'fermi',
    }

for key, value in user_0.items():
print(f”\nKey: {key}”)
print(f”Value: {value}”)

Question 13

what does .item() do

Answer 13

it returns a list of key-value pairs

Question 14

use the dictionary that compares similar values to write a for loop with f-strings

Answer 14

favorite_languages = {
    'jen': 'python',
    'sarah': 'c',
    'edward': 'ruby',
    'phil': 'python',
    }

for name, language in favorite_languages.items():
print(f”\t{name.title()}, I see you love {language}!”)

Question 15

loop through just the keys in a dictionary

Answer 15

favorite_languages = {
    'jen': 'python',
    'sarah': 'c',
    'edward': 'ruby',
    'phil': 'python',
    }

for name in favorite_languages.keys():
print(name)

Question 16

loop through a dictionary’s keys using sorted

Answer 16

favorite_languages = {
    'jen': 'python',
    'sarah': 'c',
    'edward': 'ruby',
    'phil': 'python',
    }

for name in sorted(favorite_languages.keys()):
print(f”{name.title()}, thank you for taking the poll”)

Question 17

loop through all the values in a dictionaries

Answer 17

favorite_languages = {
    'jen': 'python',
    'sarah': 'c',
    'edward': 'ruby',
    'phil': 'python',
    }

print(“the following languages have been mentioned:”)
for language in favorite_languagesvalues():
print(language.title())

Question 18

what does set() do

Answer 18

when you wrap set() around a list that contains duplicate items, Python identifies the unique items in the list and builds a set from those items

Question 19

use set() in a for loop using the dictionary with the similar values

Answer 19

favorite_languages = {
    'jen': 'python',
    'sarah': 'c',
    'edward': 'ruby',
    'phil': 'python',
    }

print(“the following languages have been mentioned:”)
for language in set(favorite_languages.values()):
print(language.title())

Question 20

build a set in a variable, and what does it look like?

Answer 20

languages = {‘python’, ‘python’, ‘ruby’, ‘c’}

print(languages)

Question 21

make 3 dictionaries and put them into a list

then use a loop to print each out

Answer 21

alien_0 = {'color': 'green', 'points': 5}
alien_1 = {'color': 'yellow', 'points': 10}
alien_0 = {'color': 'red', 'points': 15}

aliens = [alien_0, alien_1, alien_0]

for alien in aliens:
print(alien)

Question 22

use range to create 30 aliens and put them into an empty list

print how many were created using len in an f-string

Answer 22

# Make an empty list for storing aliens.
aliens = []

# Make 30 green aliens.
for alien_number in range(30):
    new_alien = {'color': 'green', 'points': 5, 'speed': 'slow'}
    aliens.append(new_alien)

# Show the first 5 aliens.
for alien in aliens[:5]:
    print(alien)
print("...")

#show how many aliens have been created
print(f"total number of of aliens {len(aliens)}")

Question 23

what is nesting

Answer 23

store multiple dictionaries in a list or a list as a value in dictionary

Question 24

use an if statement inside a for loop to modify the aliens if the color is green

Answer 24

# Make 30 green aliens.
for alien_number in range(30):
    new_alien = {'color': 'green', 'points': 5, 'speed': 'slow'}
    aliens.append(new_alien)

for alien in aliens[:3]:
    if alien['color'] == 'green':
        alien['color'] = 'yellow'
        alien['speed'] = 'medium'
        alien['points'] = 10

Question 25

use an if statement inside a for loop to modify the aliens if the color is yellow

Answer 25

# Make 30 green aliens.
for alien_number in range(30):
    new_alien = {'color': 'green', 'points': 5, 'speed': 'slow'}
    aliens.append(new_alien)

for alien in aliens[:3]:
    if alien['color'] == 'green':
        alien['color'] = 'yellow'
        alien['speed'] = 'medium'
        alien['points'] = 10
     elif alien['color'] == 'yellow':
        alien['color'] = 'red'
        alien['speed'] = 'fast'
        alien['points'] = 15

Question 26

make a pizza dictionary with crust and toppings as key, but put a list as the value for toppings

make a for loop of the toppings

Answer 26

Store information about a pizza being ordered.
pizza = {
‘crust’: ‘thick’,
‘toppings’: [‘mushrooms’, ‘extra cheese’],
}

# Summarize the order.
print(f"You ordered a {pizza['crust']}-crust pizza "
    "with the following toppings:")

for topping in pizza[‘toppings’]:
print(“\t” + topping)

Question 27

nest list in the dictionary of the favorite language

loop through the dictionary and use language as the key to hold each value from the dictionary

use another loop to run through each person’s list

decide how you want the output to be formatted

Answer 27

favorite_languages = {
    'jen': ['python', 'ruby'],
    'sarah': ['c'],
    'edward': ['ruby', 'go'],
    'phil': ['python', 'haskell'],
    }

for name, languages in favorite_languages.items():
print(f”\n{name.title()}’s favorite languages are:”)
for language in languages:
print(f”\t{Language.title()}”)

Question 28

make a dictionary with two keys and then add dictionaries for the values

the loop through the users dictionary

then print the users name

then access the information and use the keys to generate a full name and location

print a summary of what we know about the user

Answer 28

users = {
    'aeinstein': {
        'first': 'albert',
        'last': 'einstein',
        'location': 'princeton',
        },

    'mcurie': {
        'first': 'marie',
        'last': 'curie',
        'location': 'paris',
        },

}

for username, user_info in users.items():
print(f”\nUsername: {username}”)
full_name = f”{user_info[‘first’]} {user_info[‘last’]}”
location = user_info[‘location’]

print(f"\tFull name: {full_name.title()}")
print(f"\tLocation: {location.title()}")