Chapter 6: Dictionaries Flashcards
create a simple dictionary and call a value
alien_0 = {‘color’: ‘green’, ‘points’: 5}
print(alien_0[‘color’])
print(alien_0[‘points’])
what are key-value pairs
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
access a value from a dictionary by putting it into a variable and then printing an f-string
new_points = alien_0[‘points’]
print(f”You just earned {new_points} points”)
add new key-value pairs
alien_0['x_position'] = 0 alien_0['y_position'] = 25
start with an empty dictionary and fill it
alien_0 = {}
alien_0['color'] = 'green' alien_0['points'] = 5
modify the values in the dictionary
alien_0[‘color’] = ‘yellow’
print(f” The alien is now {alien_0[‘color’]}”)
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.
#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’]}”)
use the del statement to completely remove a key-value pair
alien_0 = {‘color’: ‘green’, ‘points’: 5}
del alien_0[‘points’]
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
favorite_languages = {
'jen': 'python',
'sarah': 'c',
'edward': 'ruby',
'phil': 'python',
}
language = favorite_languages[‘sarah’].title()
print(f”Sarah’s favorite language is {language}”)
what does .get()
sets a default value that will be returned if a requested key doesn’t exist
create a dictionary and use .get() to set a default value if a key doesn’t exist
alien_0 = {‘color’: ‘green’, ‘speed’: ‘slow’}
point_value = alien_0.get(‘points’, ‘No point value assigned.’)
print(point_value)
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
user_0 = {
'username': 'efermi',
'first': 'enrico',
'last': 'fermi',
}
for key, value in user_0.items():
print(f”\nKey: {key}”)
print(f”Value: {value}”)
what does .item() do
it returns a list of key-value pairs
use the dictionary that compares similar values to write a for loop with f-strings
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}!”)
loop through just the keys in a dictionary
favorite_languages = {
'jen': 'python',
'sarah': 'c',
'edward': 'ruby',
'phil': 'python',
}
for name in favorite_languages.keys():
print(name)
loop through a dictionary’s keys using sorted
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”)
loop through all the values in a dictionaries
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())
what does set() do
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
use set() in a for loop using the dictionary with the similar values
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())
build a set in a variable, and what does it look like?
languages = {‘python’, ‘python’, ‘ruby’, ‘c’}
print(languages)
make 3 dictionaries and put them into a list
then use a loop to print each out
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)
use range to create 30 aliens and put them into an empty list
print how many were created using len in an f-string
# 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)}")
what is nesting
store multiple dictionaries in a list or a list as a value in dictionary
use an if statement inside a for loop to modify the aliens if the color is green
# 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
use an if statement inside a for loop to modify the aliens if the color is yellow
# 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
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
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)
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
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()}”)
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
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()}")
