How to slice a Sub-array from a reshaped 1D NumPy array and print strides?

Last update on March 26 2025 13:18:39 (UTC/GMT +8 hours)

16. Sub-array Strides Inspection

Write a NumPy program that creates a 1D array of 15 elements, reshape it into a (3, 5) matrix, then slice a sub-array from it and print the sub-array and its strides.

Sample Solution:

Python Code:

import numpy as np

# Create a 1D array of 15 elements
array_1d = np.arange(1, 16)

# Reshape the 1D array into a (3, 5) matrix
matrix_3x5 = array_1d.reshape(3, 5)

# Slice a sub-array from the matrix (e.g., select rows 1 and 2, columns 2 to 4)
sub_array = matrix_3x5[1:3, 2:5]

# Print the sub-array
print("Sub-array:\n", sub_array)

# Print the strides of the sub-array
print("Strides of the sub-array:", sub_array.strides)

Output:

Sub-array:
 [[ 8  9 10]
 [13 14 15]]
Strides of the sub-array: (20, 4)

Explanation:

• Import NumPy library: We start by importing the NumPy library to handle array operations.
• Create a 1D array: We create a 1D array array_1d with 15 elements using np.arange(1, 16).
• Reshape to (3, 5) matrix: We reshape the 1D array to a (3, 5) matrix matrix_3x5 using reshape().
• Slice a sub-array: We slice a sub-array from matrix_3x5 by selecting rows 1 and 2, and columns 2 to 4, resulting in sub_array.
• Print the sub-array: We print sub_array to display the sliced portion of the original matrix.
• Print strides of sub-array: We print the strides of sub_array using the strides attribute to understand its memory layout.

For more Practice: Solve these Related Problems:

• Write a NumPy program to extract various sub-arrays from a reshaped array and print their strides to analyze the impact of slicing.
• Write a NumPy program to create a 2D array, take a diagonal slice, and print its strides compared to the original array.
• Write a NumPy program to extract a sub-array using slicing with a step and compare its strides with standard slicing.
• Write a NumPy program to create a 2D array, perform multiple slices, and analyze how the strides change with each slicing operation.

Python-Numpy Code Editor:

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