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Python Loops Tutorial
course content

Course Content

Python Loops Tutorial

Python Loops Tutorial

1. The for Loop
The First for LoopIterating with range() FunctionChallenge: Exploring Steps and Reverse with range()The if/else Statements in a for LoopCounting 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
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.

Example: Creating a New List Using a Traditional for Loop

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.

So, you need a list with city names only, without countries and trip costs.

For that task you can use for loop:


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

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

print(city_names)  # Output: ['Paris', 'Tokyo', 'New York', 'Kyoto', 'Sydney']
copy

Example: Creating a New List Using List Comprehension

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)  # Output: ['Paris', 'Tokyo', 'New York', 'Kyoto', 'Sydney']
copy

Explanation:

  • 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
test

Swipe to begin your solution

You are managing a travel wishlist, and you need to create a new list that contains only the trip costs (the third element) from each destination in the wishlist.

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 1
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book
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.

Example: Creating a New List Using a Traditional for Loop

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.

So, you need a list with city names only, without countries and trip costs.

For that task you can use for loop:


              
12345678910111213

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

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

print(city_names)  # Output: ['Paris', 'Tokyo', 'New York', 'Kyoto', 'Sydney']
copy

Example: Creating a New List Using List Comprehension

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)  # Output: ['Paris', 'Tokyo', 'New York', 'Kyoto', 'Sydney']
copy

Explanation:

  • 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
test

Swipe to begin your solution

You are managing a travel wishlist, and you need to create a new list that contains only the trip costs (the third element) from each destination in the wishlist.

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 1
Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
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