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Count how many zeros you have in array

Posted on May 5, 2021April 5, 2022 By Luke K

Let’s learn how to count how many zeros you have in array. There are two different Python methods you can use.
Numpy count zeros

Using a count_nonzero method

We will use really unexpected Numpy method. For sure you will be surprised. To count a zeros frequency in your matrix you need to use count_nonzero function. Then as a parameter you should use your array == 0. Believe me it works.

import numpy as np

my_array = np.array([[1, 0, 5],
                    [5, 3, 0],
                    [0, 0, 2]])

zeros_frequency = np.count_nonzero(my_array == 0)
print(f"Count of zeroes in my array: \n{zeros_frequency}")

Numpy count zeros

As you can see count_nonzero function counted zeros.

See also  How to shuffle an array in Numpy?

Using a where method

The second way to calculate zeros in an array is to use where Python method.

import numpy as np

my_array = np.array([[1, 0, 5],
                    [5, 3, 0],
                    [0, 0, 2]])

zeros_frequency = my_array[np.where(my_array == 0)].size
print(f"There are {zeros_frequency} zeros in my array.")

This time zeros_frequency will provide an array of zeros. To calculate the number of zeros simply, you need to return the size of that array.

See also  How to check for nan in array?

The output is the same.

There are 4 zeros in my array.
numpy Tags:array, count, number, zero

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