List Introduction

Lecture 14:- List Introduction

In Python, a list is a versatile and widely used data structure that allows you to store a collection of elements in a single variable. Lists are mutable, meaning you can modify their content after they are created. Lists are defined by enclosing a comma-separated sequence of elements within square brackets [ ].

Here's a brief introduction to lists in Python:

1. Creating a List: You can create a list by defining it with square brackets and including the elements separated by commas.

Example:

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# List of integers numbers = [1, 2, 3, 4, 5] # List of strings fruits = ["apple", "banana", "orange"] # Mixed data types mixed_list = [10, "hello", 3.14, True]

1. Accessing Elements: You can access individual elements in a list using their index. The index of the first element is 0, the second element is 1, and so on. You can also use negative indices to access elements from the end of the list.

Example:

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

1. List Slicing: You can extract a portion of a list using slicing. Slicing allows you to get a sublist based on a range of indices.

Example:

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numbers = [1, 2, 3, 4, 5, 6, 7] print(numbers[1:4])   # Output: [2, 3, 4] (elements from index 1 to 3) print(numbers[:3])    # Output: [1, 2, 3] (elements from the beginning to index 2) print(numbers[3:])    # Output: [4, 5, 6, 7] (elements from index 3 to the end)

1. Modifying Lists: Lists are mutable, so you can change, add, or remove elements after creating the list.

Example:

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fruits = ["apple", "banana", "orange"] fruits[0] = "pear"    # Modify the first element print(fruits)         # Output: ["pear", "banana", "orange"] fruits.append("grape")  # Add an element at the end print(fruits)           # Output: ["pear", "banana", "orange", "grape"] fruits.remove("banana")  # Remove a specific element print(fruits)            # Output: ["pear", "orange", "grape"]

1. List Methods: Lists come with various built-in methods to perform common operations, such as append(), extend(), insert(), pop(), sort(), reverse(), etc. These methods provide convenient ways to manipulate lists.

Lists are fundamental data structures in Python, and their versatility makes them suitable for a wide range of applications. They are commonly used to hold collections of items, process data, and perform various tasks in Python programming.