Dictionary Comprehensions

Dictionary comprehensions provide a concise way to create dictionaries in Python, similar to list comprehensions. They enable you to transform data into key-value pairs in a single line of code.

At its heart, a basic dictionary comprehension lets you construct a new dictionary by applying an expression to each key-value pair in an iterable variable. The syntax:

key_expression: defines the key for each key-value pair;
value_expression: defines the value corresponding to the key;
iterable: the source of items to be processed (e.g., a list, range, or another iterable).


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travel_wishlist = [
    ["Paris", 2000],
    ["Tokyo", 3000],
    ["New York", 2500],
    ["Kyoto", 1500],
    ["Sydney", 4000]
]

# Initialize an empty dictionary
travel_budget = {}

# Populate the dictionary using a for loop
for destination, cost in travel_wishlist:
    travel_budget[destination] = cost

print(travel_budget)

Description:

This code iterates through the travel_wishlist list, where each sublist contains a destination and its budget. The for loop assigns the destination as the key and the budget as the value in the travel_budget dictionary.

Example: Creating a Travel Budget Dictionary Using Dictionary Comprehension


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travel_wishlist = [
    ["Paris", 2000],
    ["Tokyo", 3000],
    ["New York", 2500],
    ["Kyoto", 1500],
    ["Sydney", 4000]
]

# Create the dictionary using dictionary comprehension
travel_budget = {destination: cost for destination, cost in travel_wishlist}

print(travel_budget)

Description:

This example uses dictionary comprehension to achieve the same result as the previous example. Each destination becomes a key, and its corresponding cost becomes the value in the travel_budget dictionary, all in a single line.

Task

Swipe to start coding

A traveler wants to create a dictionary that maps city names to their corresponding countries. Use dictionary comprehension to create a new dictionary called city_to_country from the following travel_wishlist:

Transform the travel_wishlist list into a dictionary where the city is the key and the country is the value.

Solution

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Section 4. Chapter 3

Dictionary Comprehensions

Dictionary comprehensions provide a concise way to create dictionaries in Python, similar to list comprehensions. They enable you to transform data into key-value pairs in a single line of code.

At its heart, a basic dictionary comprehension lets you construct a new dictionary by applying an expression to each key-value pair in an iterable variable. The syntax:

key_expression: defines the key for each key-value pair;
value_expression: defines the value corresponding to the key;
iterable: the source of items to be processed (e.g., a list, range, or another iterable).


              12345678910111213141516
            
travel_wishlist = [
    ["Paris", 2000],
    ["Tokyo", 3000],
    ["New York", 2500],
    ["Kyoto", 1500],
    ["Sydney", 4000]
]

# Initialize an empty dictionary
travel_budget = {}

# Populate the dictionary using a for loop
for destination, cost in travel_wishlist:
    travel_budget[destination] = cost

print(travel_budget)

Description:

Example: Creating a Travel Budget Dictionary Using Dictionary Comprehension


              123456789101112
            
travel_wishlist = [
    ["Paris", 2000],
    ["Tokyo", 3000],
    ["New York", 2500],
    ["Kyoto", 1500],
    ["Sydney", 4000]
]

# Create the dictionary using dictionary comprehension
travel_budget = {destination: cost for destination, cost in travel_wishlist}

print(travel_budget)

Description:

Task

Swipe to start coding

Transform the travel_wishlist list into a dictionary where the city is the key and the country is the value.

Solution

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 4. Chapter 3

Switch to desktop for real-world practiceContinue from where you are using one of the options below