NumPy: Extract first, third and fifth elements of the third and fifth rows from a given (6x6) array

Last update on August 29 2025 12:49:34 (UTC/GMT +8 hours)

Extract First, Third, Fifth Elements of Third/Fifth Rows of 6x6 Array

Write a NumPy program to extract the first, third and fifth elements of the third and fifth rows from a given (6x6) 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 35 and reshaping it into a 6x6 matrix
arra_data = np.arange(0, 36).reshape((6, 6))

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

# Printing the original 6x6 array 'arra_data'
print(arra_data)

# Displaying a message indicating the extracted data (First, third, and fifth elements of the third and fifth rows)
print("\nExtracted data: First, third, and fifth elements of the third and fifth rows")

# Using slicing to extract a sub-array containing the first, third, and fifth elements of the third and fifth rows
print(arra_data[2::2, ::2])

Sample Output:

Original array:
[[ 0  1  2  3  4  5]
 [ 6  7  8  9 10 11]
 [12 13 14 15 16 17]
 [18 19 20 21 22 23]
 [24 25 26 27 28 29]
 [30 31 32 33 34 35]]

Extracted data: First, third and fifth elements of the third and fifth rows
[[12 14 16]
 [24 26 28]]

Explanation:

In the above exercise -

arra_data = np.arange(0, 36).reshape((6, 6)): This line creates a 1-dimensional NumPy array with elements from 0 to 35 (excluding 36) using np.arange(0, 36) and then reshapes it into a 2-dimensional array with 6 rows and 6 columns using .reshape((6, 6)).

print(arra_data[2::2, ::2]): It prints a subarray of ‘arra_data’ by selecting rows starting from index 2 with a step of 2, and columns starting from index 0 with a step of 2 using slicing with a step.

The subarray consists of the elements at rows 2 and 4 and columns 0, 2, and 4 in the original array ‘arra_data’.

For more Practice: Solve these Related Problems:

• Write a NumPy program to extract non-consecutive elements (first, third, and fifth) from specified rows of a 6x6 array.
• Create a function that uses advanced indexing to return selected elements from the third and fifth rows.
• Test the extraction on a 6x6 array by comparing the output with manually calculated indices.
• Implement a solution that uses np.take with a custom index array to extract the desired columns.

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