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Program 1

Array Indexing and Slicing

1D Array

Output 1

Program 2

Array Indexing and Slicing

2D Array

import numpy as np

# Create a 2D NumPy array (3x4)
arr = np.array([[10, 20, 30, 40],
                [50, 60, 70, 80],
                [90, 100, 110, 120]])

# Indexing - accessing specific elements
first_element = arr[0, 0]       # Element at first row, first column
middle_element = arr[1, 2]      # Element at second row, third column (70)
last_element = arr[2, 3]        # Element at third row, fourth column (120)

# Slicing - accessing multiple elements
slice_row_1 = arr[0, :]         # All elements of the first row
slice_column_2 = arr[:, 1]      # All elements of the second column
slice_1 = arr[0:2, 1:3]         # First two rows and columns 1 to 2
slice_2 = arr[1:, 2:]           # From second row to the end, and columns 2 to end
slice_step = arr[::2, ::2]      # Every second row and second column
reverse_array = arr[::-1, ::-1] # Reverse rows and columns

# More complex slicing
row_1_column_1_and_3 = arr[0, [1, 3]]  # Elements from the first row, second and fourth column
row_2_and_3_column_1_and_3 = arr[[1, 2], [1, 3]] # Elements at positions (1,1) and (2,3)

# Output the results
print("Original array:\n", arr)
print("\nIndexing:")
print("\nFirst element (arr[0, 0]):\n", first_element)
print("\nMiddle element (arr[1, 2]):\n", middle_element)
print("\nLast element (arr[2, 3]):\n", last_element)

print("\nSlicing:")
print("\nAll elements of the first row (arr[0, :]):\n", slice_row_1)
print("\nAll elements of the second column (arr[:, 1]):\n", slice_column_2)
print("\nFirst two rows and columns 1 to 2 (arr[0:2, 1:3]):\n", slice_1)
print("\nFrom second row onwards and columns 2 onwards (arr[1:, 2:]):\n", slice_2)
print("\nEvery second row and column (arr[::2, ::2]):\n", slice_step)
print("\nReversed array (rows and columns reversed):\n", reverse_array)

print("\nAdvanced Slicing:")
print("\nElements from first row, columns 2 and 4 (arr[0, [1, 3]]):\n", row_1_column_1_and_3)
print("\nElements at positions (1,1) and (2,3) (arr[[1, 2], [1, 3]]):\n", row_2_and_3_column_1_and_3)

Output 2

Introduction to Numpy

Array Indexing and Slicing

Array Indexing and Slicing