Python:NumPy .nonzero()

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Published Nov 15, 2025
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The .nonzero() method returns the indices of elements in a NumPy array that are non-zero or evaluate to True. It is often used to locate positions of meaningful or valid data within an array.

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Syntax

ndarray.nonzero()

Parameters:

This method takes no parameters.

Return value:

Returns a tuple of arrays, one for each dimension, containing the indices of elements that are non-zero.

Example: Finding Non-Zero Elements in a 1D Array

In this example, the indices of all non-zero elements in a 1D NumPy array are returned:

import numpy as np


arr = np.array([0, 2, 0, 4, 5])
result = arr.nonzero()
print(result)

The output of this code is:

(array([1, 3, 4]),)

Codebyte Example

In this example, the positions of non-zero elements in a 2D array are identified:

Code
Output
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  • Career path
    Data Scientist: Machine Learning Specialist
    Machine Learning Data Scientists solve problems at scale, make predictions, find patterns, and more! They use Python, SQL, and algorithms.
    • Includes 27 Courses
    • With Professional Certification
    • Beginner Friendly.
      95 hours
  • Course
    Learn Python 3
    Learn the basics of Python 3.12, one of the most powerful, versatile, and in-demand programming languages today.

    • With Certificate
    • Beginner Friendly.
      24 hours