.shuffle()

DanielCrigan's avatar
DanielCrigan's avatar
DanielCrigan
Published May 19, 2025
Contribute to Docs

In Numpy random module, the .shuffle() function randomly rearranges the elements of an array or sequence. It modifies the original array in place, altering its contents directly.

Syntax

The general syntax for .shuffle() is:

np.random.shuffle(x)

Parameters:

  • x: The input array or sequence to be shuffled.
    • For 1D arrays, the entire array is shuffled.
    • For multi-dimensional arrays, only the first axis is shuffled (e.g., rows in a 2D array).

Return value:

  • This function modifies the input array in place and does not return a new array.

Example 1: Shuffling a 1D Array

In this example, the np.random.shuffle() randomly permutates elements of an array, enabling shuffling of data in-place:

# Import NumPy
import numpy as np


# Create an array of integers
arr = np.array([1, 2, 3, 4, 5])
print("Original Array:", arr)


# Shuffle the array in-place
np.random.shuffle(arr)
print("Shuffled Array:", arr)

This could could result in the following possible output:

Original Array: [1 2 3 4 5]
Shuffled Array: [3 1 5 2 4]

Note: The output differs with each execution, as the elements are shuffled randomly in-place.

Example 2: Shuffling a 2D Array (Rows Only)

In this example, np.random.shuffle() randomly reorders the rows of a 2D array, modifying it in place. Note that only the rows (first axis) are shuffled, not the individual elements within each row:

import numpy as np


# Create a 2D array
arr_2d = np.array([[10, 20], [30, 40], [50, 60]])
print("Original 2D Array:\n", arr_2d)


# Shuffle rows in-place
np.random.shuffle(arr_2d)
print("Shuffled 2D Array:\n", arr_2d)

A possible output of this code can be:

Original 2D Array:
 [[10 20]
 [30 40]
 [50 60]]
Shuffled 2D Array:
 [[50 60]
 [10 20]
 [30 40]]

Note: The order of rows will differ each time the code is executed, as the shuffling is random and in-place.

Codebyte Example: Shuffling Survey Responses and Questions

In this example, a survey system uses np.random.shuffle() to randomize both survey responses (1D array) and questions (2D array) to avoid bias in responses:

Code
Output
Loading...


All contributors
Contribute to Docs
Learn Python:NumPy on Codecademy