Indexing

Indexing is the process of accessing individual elements within a sequence, such as a string, list, or tuple, using their position or index number.

How Indexing Works

·         Python uses zero-based indexing, meaning the first element has an index of 0, the second has an index of 1, and so on.

·         You access elements using square brackets [] with the index inside.

Example with a List

Python

my_list = [10, 20, 30, 40]

first_element = my_list[0]  # Accesses the first element (10)

third_element = my_list[2]  # Accesses the third element (30)

Example with a String

Python

my_string = "Python"

first_character = my_string[0]  # Accesses the first character ('P')

last_character = my_string[-1]  # Accesses the last character ('n')

Negative Indexing

You can use negative indices to access elements from the end of a sequence:

Python

my_list = [10, 20, 30, 40]

last_element = my_list[-1]  # Accesses the last element (40)

Slicing

Indexing can also be used for slicing, which extracts a portion of a sequence:

Python

my_list = [10, 20, 30, 40, 50]

sublist = my_list[1:4]  # Extracts elements from index 1 to 3 (exclusive)

Key Points

·         Indexing starts from 0.

·         Negative indices access elements from the end.

·         Slicing creates a new sequence.

·         Be careful with index out of range errors.

By understanding indexing, you can effectively manipulate and access elements within sequences in Python.