Python - Arrays

In Python, you can access elements in a list (or array) using indexing. The index represents the position of an element in the list, and it starts from 0 for the first element. Negative indexing is also allowed, with -1 representing the last element, -2 representing the second-to-last element, and so on.

Here is an example program demonstrating how to access elements in a list using indexing:

# Create a list
my_list = [10, 20, 30, 40, 50]

# Access elements using positive indexing
first_element = my_list[0]
second_element = my_list[1]

# Access elements using negative indexing
last_element = my_list[-1]
second_to_last_element = my_list[-2]

# Display the accessed elements
print("First Element:", first_element)
print("Second Element:", second_element)
print("Last Element:", last_element)
print("Second-to-Last Element:", second_to_last_element)

Output:

First Element: 10
Second Element: 20
Last Element: 50
Second-to-Last Element: 40

In this example, the list my_list is created, and elements are accessed using both positive and negative indexing.

In Python, a multidimensional array is essentially a list of lists, where each element in the outer list is a list representing a row or sub-array. This structure allows you to create arrays with multiple dimensions (rows and columns).

Here is an example program demonstrating the concept of multidimensional arrays:

# Create a 2D array (3x3)
matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

# Access elements in the 2D array
element_1_2 = matrix[1][2]

# Display the accessed element
print("Element at row 1, column 2:", element_1_2)

Output:

Element at row 1, column 2: 6

In this example, matrix is a 2D array, and we access an element at row 1, column 2 using indexing.

You can check the length of an array in Python using the len() function. Here is an example program demonstrating how to check the length of an array:

# Create an array
my_array = [1, 2, 3, 4, 5]

# Check the length of the array
array_length = len(my_array)

# Display the length
print("Length of the array:", array_length)

Output:

Length of the array: 5

In this example, the len() function is used to determine the number of elements in the array my_array.

Slicing is a technique in Python that allows you to extract a portion of an array. It is done using the colon (:) operator. Here's an example program demonstrating the use of slicing with arrays:

# Create an array
my_array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

# Slice the array to get elements from index 2 to 5 (excluding 5)
sliced_array = my_array[2:5]

# Display the sliced array
print("Sliced Array:", sliced_array)

Output:

Sliced Array: [3, 4, 5]

In this example, the array my_array is sliced using the syntax my_array[start:stop]. The resulting sliced_array includes elements from index 2 to 4 (excluding 5).