NumPy: Extract all the elements of the third column from a given (4x4) array

Last update on March 24 2025 13:36:26 (UTC/GMT +8 hours)

Extract Third Column of 4x4 Array

Write a NumPy program to extract all the third column elements from a given (4x4) array.

Pictorial Presentation:

Sample Solution:

Python Code:

# Importing the NumPy library and aliasing it as 'np'
import numpy as np

# Creating a NumPy array 'arra_data' containing integers from 0 to 15 and reshaping it into a 4x4 matrix
arra_data = np.arange(0, 16).reshape((4, 4))

# Displaying a message indicating the original array will be printed
print("Original array:")

# Printing the original 4x4 array 'arra_data'
print(arra_data)

# Displaying a message indicating the extracted data (third column)
print("\nExtracted data: Third column")

# Printing the third column of the 'arra_data' array using column indexing
print(arra_data[:, 2])

Sample Output:

Original array:
[[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]
 [12 13 14 15]]

Extracted data: Third column
[ 2  6 10 14]

Explanation:

arra_data = np.arange(0, 16).reshape((4, 4)): It creates a 1-dimensional NumPy array with elements from 0 to 15 (excluding 16) using np.arange(0, 16) and then reshapes it into a 2-dimensional array with 4 rows and 4 columns using .reshape((4, 4)).

print(arra_data[:, 2]): This line prints the third column of the array ‘arra_data’. In this case, it will print [ 2, 6, 10, 14]. The colon : indicates that all rows should be included, and the index 2 corresponds to the third column in the array.

For more Practice: Solve these Related Problems:

• Write a NumPy program to extract the third column from a 4x4 array using slicing with colon notation.
• Create a function that retrieves any specified column from a 2D array and confirms its content.
• Test column extraction on arrays of different sizes to ensure consistent behavior with negative indexing.
• Implement an alternative approach using np.take with axis 1 and compare it to the slicing method.

Python-Numpy Code Editor: