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List Comprehensions

List comprehensions are a powerful way to create new lists by combining loops and optional conditions into a single, concise statement. They provide a more Pythonic way to perform operations on lists, making your code cleaner and easier to read.

Let's start with a simple example. You have a travel_wishlist containing cities you want to visit, each represented as a nested list with its name, country, and trip cost.


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travel_wishlist = [
    ['Paris', 'France', 2000],
    ['Tokyo', 'Japan', 3000],
    ['New York', 'USA', 2500],
    ['Kyoto', 'Japan', 1500],
    ['Sydney', 'Australia', 4000]
]

city_names = []  # New empty list
for city in travel_wishlist:
    city_names.append(city[0])

print(city_names)

Here, the list comprehension does the same job in a single line, making it concise and readable.


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travel_wishlist = [
    ['Paris', 'France', 2000],
    ['Tokyo', 'Japan', 3000],
    ['New York', 'USA', 2500],
    ['Kyoto', 'Japan', 1500],
    ['Sydney', 'Australia', 4000]
]

city_names = [city[0] for city in travel_wishlist]

print(city_names)

The travel_wishlist is a list of lists, where each inner list contains the city name, country, and estimated budget for a trip;
The code [city[0] for city in travel_wishlist] creates a new list by extracting the first element (city[0], the city name) from each inner list in travel_wishlist.

Task

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You are managing a travel_wishlist, where each destination is represented as a list containing multiple details. Your goal is to extract only the trip costs from each destination and store them separately.

Iterate through the wishlist, accessing each destination's details.
Extract the trip cost, which is the third element in each destination's list.
Store the extracted costs in a new list called trip_costs.

Solution

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Section 4. Chapter 1

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List Comprehensions

Let's start with a simple example. You have a travel_wishlist containing cities you want to visit, each represented as a nested list with its name, country, and trip cost.


              12345678910111213
            
travel_wishlist = [
    ['Paris', 'France', 2000],
    ['Tokyo', 'Japan', 3000],
    ['New York', 'USA', 2500],
    ['Kyoto', 'Japan', 1500],
    ['Sydney', 'Australia', 4000]
]

city_names = []  # New empty list
for city in travel_wishlist:
    city_names.append(city[0])

print(city_names)

Here, the list comprehension does the same job in a single line, making it concise and readable.


              1234567891011
            
travel_wishlist = [
    ['Paris', 'France', 2000],
    ['Tokyo', 'Japan', 3000],
    ['New York', 'USA', 2500],
    ['Kyoto', 'Japan', 1500],
    ['Sydney', 'Australia', 4000]
]

city_names = [city[0] for city in travel_wishlist]

print(city_names)

The travel_wishlist is a list of lists, where each inner list contains the city name, country, and estimated budget for a trip;
The code [city[0] for city in travel_wishlist] creates a new list by extracting the first element (city[0], the city name) from each inner list in travel_wishlist.

Task

Swipe to start coding

Iterate through the wishlist, accessing each destination's details.
Extract the trip cost, which is the third element in each destination's list.
Store the extracted costs in a new list called trip_costs.

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 1

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