Course Content

Python Data Structures

1. Mastering Python Lists

Creating Lists in Python: Declaring and Initializing Lists List Indexing in Python: Accessing Elements Efficiently Working with Nested Lists in Python Python List Length: Measuring and Managing List Size Modifying Lists in Python: Updating and Changing Elements Using the append() Method: Adding Elements to Lists Using the insert() Method: Placing Elements at Specific Positions Deleting Elements in Python Lists: Removing Items Safely Using the remove() Method: Deleting Specific Elements from Lists

2. Mastering Python Dictionaries

Creating a Dictionary in Python: Storing Key-Value Pairs Accessing Dictionary Values Accessing Dictionary Keys Adding Items to a Dictionary: Updating Key-Value Pairs Using the del Keyword: Removing Dictionary Entries Using the pop() Method: Deleting Elements with Return Values Using the popitem() Method: Removing the Last Inserted Item Using the clear() Method: Emptying a Dictionary Completely

3. Mastering Python Tuples

Creating a Tuple in Python: Defining Immutable Data Structures Accessing Elements in a Tuple: Indexing Technique Concatenating Tuples in Python: Merging Immutable Sequences Deleting Tuples in Python: Removing References to Tuples Updating Tuples in Python Adding Items to a Tuple: Alternative Approaches Using Lists Counting Elements in a Tuple: Using the count() Method Finding Elements in a Tuple: Using the index() Method for Lookup

4. Mastering Python Sets

Creating a Set in Python: Defining Unordered Collections Using the add() Method: Adding Single Elements to a Set Using the update() Method: Merging Multiple Elements into a Set Accessing Elements in a Set: Iteration and Membership Testing Using the remove() and discard() Methods Using the clear() Method: Removing All Elements from a Set

List Indexing in Python: Accessing Elements Efficiently

In Python, lists allow you to access individual elements using their index. Indexing starts at 0, meaning the first element in a list is at index 0, the second element is at index 1, and so on. This is called zero indexing. To access an element, use square brackets with the index of the desired item.


              1234567
            
cities = ["Rome", "London", "New York", "Brasilia", "Kioto"]

# Getting the first element
print(cities[0])

# Getting the third element
print(cities[2])

In the next example, the index 0 returns the first element, 'Rome', while the index 2 returns the third element, which is 'New York'. Remember that the index corresponds to the position minus one (n - 1).

Negative Indexing

Python also supports negative indexing: this allows you to access elements from the end of the list. Here, -1 represents the last item, -2 represents the second last item, and so on. Negative indexing can be very useful when you want to work with a list from the end without knowing its length.


              1234567
            
cities = ["Rome", "London", "New York", "Brasilia", "Kioto"]

# Getting the last element
print(cities[-1])

# Getting the fourth element
print(cities[3], cities[-2])

Explanation:

-1 retrieves the last element 'Kioto';
3 and -2 both refer to the fourth element 'Brasilia', one using positive indexing and the other using negative indexing. This demonstrates how indexing wraps around the list.

Positive and negative indexing add versatility to the access of elements from lists, either from the beginning or the end.

Indexing in Nested Lists

Accessing elements in a nested list requires multiple indices: the first index selects the sublist, and the second index accesses the specific item within that sublist.


              1234567891011121314
            
cities = [
    ["Paris", "France", 2000], 
    ["Tokyo", "Japan", 3000], 
    ["New York", "USA", 2500]
]

# Accessing the first sublist
print(cities[0])  # Output: ['Paris', 'France', 2000]

# Accessing the city name in the second sublist
print(cities[1][0])  # Output: Tokyo

# Accessing the cost of the trip in the third sublist
print(cities[2][2])  # Output: 2500

Applications of nested list indexing include but are not limited to, structured data such as spreadsheets, matrices, or databases. Practical examples could be accessing rows and columns in a 2D matrix, retrieving details from lists of employee records, or extracting specific information, such as the city names or costs from travel itineraries or nested JSON-like structures.

Task

Swipe to start coding

You are given a list named cities.

Initialize the variable second with the second element of the array using the index.
Initialize the variable last with the last element of the array using the index.

Note

You can use a negative index for easier access to the last element.

Solution

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Section 1. Chapter 2

List Indexing in Python: Accessing Elements Efficiently


              1234567
            
cities = ["Rome", "London", "New York", "Brasilia", "Kioto"]

# Getting the first element
print(cities[0])

# Getting the third element
print(cities[2])

Negative Indexing


              1234567
            
cities = ["Rome", "London", "New York", "Brasilia", "Kioto"]

# Getting the last element
print(cities[-1])

# Getting the fourth element
print(cities[3], cities[-2])

Explanation:

-1 retrieves the last element 'Kioto';
3 and -2 both refer to the fourth element 'Brasilia', one using positive indexing and the other using negative indexing. This demonstrates how indexing wraps around the list.

Positive and negative indexing add versatility to the access of elements from lists, either from the beginning or the end.

Indexing in Nested Lists

Accessing elements in a nested list requires multiple indices: the first index selects the sublist, and the second index accesses the specific item within that sublist.


              1234567891011121314
            
cities = [
    ["Paris", "France", 2000], 
    ["Tokyo", "Japan", 3000], 
    ["New York", "USA", 2500]
]

# Accessing the first sublist
print(cities[0])  # Output: ['Paris', 'France', 2000]

# Accessing the city name in the second sublist
print(cities[1][0])  # Output: Tokyo

# Accessing the cost of the trip in the third sublist
print(cities[2][2])  # Output: 2500

Task

Swipe to start coding

You are given a list named cities.

Initialize the variable second with the second element of the array using the index.
Initialize the variable last with the last element of the array using the index.

Note

You can use a negative index for easier access to the last element.

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 1. Chapter 2

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