Learn Dictionary Comprehensions | List and 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.

{key_expression: value_expression for item in iterable}

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)

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.


              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)

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 organize their travel_wishlist by mapping each city name to its corresponding country. To achieve this efficiently, you need to transform the data into a dictionary.

Extract city names and their corresponding countries from travel_wishlist.
Store the resulting dictionary in city_to_country.

Solution

Everything was clear?

Thanks for your feedback!

Section 4. Chapter 3

single

Ask AI

Ask anything or try one of the suggested questions to begin our chat

Suggested prompts:

Can you explain how dictionary comprehensions differ from list comprehensions?

Can you show more examples of dictionary comprehensions?

What are some common use cases for dictionary comprehensions?

Swipe to show menu

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.

{key_expression: value_expression for item in iterable}

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)


              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)

Task

Swipe to start coding

A traveler wants to organize their travel_wishlist by mapping each city name to its corresponding country. To achieve this efficiently, you need to transform the data into a dictionary.

Extract city names and their corresponding countries from travel_wishlist.
Store the resulting dictionary in city_to_country.

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

single

Dictionary Comprehensions

Solution

Awesome!

Dictionary Comprehensions

Solution

Awesome!