Output of Python Program | Set 6 (Lists)

Output of Python Program | Set 6 (Lists)

Lists are one of the most versatile and widely used data structures in Python. Understanding how lists behave through different operations and manipulations is essential for mastering Python programming. In this blog, we will explore some example programs that demonstrate the output of various list operations, helping you grasp their inner workings clearly.

Basic List Creation and Access

Creating lists and accessing elements by their index is fundamental. Let's see a simple example:

my_list = [10, 20, 30, 40, 50]
print(my_list[2])  # Output will be 30
print(my_list[-1]) # Output will be 50

In this code, my_list[2] returns the third element (indexing starts at 0), which is 30. Negative indexing allows accessing elements from the end, so my_list[-1] gives the last item, 50.

List Modification

Lists are mutable, meaning you can change their content. Here’s how to update and delete elements:

numbers = [1, 2, 3, 4, 5]
numbers[0] = 10
print(numbers)  # Output: [10, 2, 3, 4, 5]

del numbers[3]
print(numbers)  # Output: [10, 2, 3, 5]

The above example replaces the first element with 10 and deletes the fourth element (index 3).

List Slicing

Slicing is a powerful feature that lets you extract parts of a list:

colors = ['red', 'green', 'blue', 'yellow', 'purple']
print(colors[1:4])  # Output: ['green', 'blue', 'yellow']
print(colors[:3])   # Output: ['red', 'green', 'blue']
print(colors[2:])   # Output: ['blue', 'yellow', 'purple']

This extracts sublists starting and ending at specified indexes.

Practice Problem

Try your hand at this exercise to strengthen your understanding:

# Practice Problem:
# Given a list of numbers, write a Python program to replace all even numbers with their squares 
# and remove all odd numbers from the list.

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

# Your code here

print(numbers)  # Expected output: [4, 16, 36, 64, 100]

Give it a try and see if you can modify the list as required!

Solution to Practice Problem

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

# Use list comprehension to replace even numbers with their squares and filter out odd numbers
numbers = [x**2 for x in numbers if x % 2 == 0]

print(numbers)  # Output: [4, 16, 36, 64, 100]

This code efficiently squares each even number and excludes the odd numbers using list comprehension.

Summary

In this blog, we explored various aspects of Python lists including indexing, modification, deletion, slicing, and practice problems to reinforce these concepts. Mastering list operations is critical for efficient Python programming, so practicing with examples like these is highly recommended.