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Learn Dictionary Comprehensions | List and Dictionary Comprehensions
Python Loops Tutorial
course content

Course Content

Python Loops Tutorial

Python Loops Tutorial

1. The For Loop
2. The while Loop
3. Nested Loops
4. List and Dictionary Comprehensions

book
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: 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)
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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.

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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)
copy

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

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Section 4. Chapter 3
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book
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: 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)
copy

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)
copy

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

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Everything was clear?

How can we improve it?

Thanks for your feedback!

Section 4. Chapter 3
Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
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