Notice: This page requires JavaScript to function properly.
Please enable JavaScript in your browser settings or update your browser.Learn Dictionary Comprehensions | List and Dictionary Comprehensions
Python Loops Tutorial
course content

Course Content

Python Loops Tutorial

Python Loops Tutorial

1. The For Loop
The First For LoopIterating with range() FunctionCounting with LoopsLoop Control StatementsThe Else Statement in a for LoopThe enumerate() Function
2. The while Loop
The First while LoopInfinite LoopUsing Condition Statements in a while LoopLoop Control Statements in a while LoopThe else Statement in a while LoopChoosing Between for and while Loops in Python
3. Nested Loops
Nested for LoopNested while Loopif/else in a Nested Loopbreak/continue in a Nested Loop
4. List and Dictionary Comprehensions
List ComprehensionsList Comprehansions with ConditionsDictionary ComprehensionsDictionary Comprehension with Condition

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.

python
  • 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!

SectionΒ 4. ChapterΒ 3
toggle bottom row

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.

python
  • 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!

SectionΒ 4. ChapterΒ 3
Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
We're sorry to hear that something went wrong. What happened?
some-alt