You can use the following basic syntax to replace negative values with zero in NumPy:

my_array[my_array <0] = 0

This syntax works with both 1D and 2D NumPy arrays.

The following examples show how to use this syntax in practice.

Example 1: Replace Negative Values with Zero in 1D NumPy Array

The following code shows how to replace all negative values with zero in a NumPy array:

import numpy as np

#create 1D NumPy array
my_array = np.array([4, -1, 6, -3, 10, 11, -14, 19, 0])

#replace negative values with zero in array
my_array[my_array <0] = 0

#view updated array
print(my_array)

[ 4  0  6  0 10 11  0 19  0]

Notice that each negative value in the original array has been replaced with zero.

Example 2: Replace Negative Values with Zero in 2D NumPy Array

Suppose we have the following 2D NumPy array:

import numpy as np

#create 2D NumPy array
my_array = np.array([3, -5, 6, 7, -1, 0, -5, 9, 4, 3, -5, 1]).reshape(4,3)

#view 2D NumPy array
print(my_array)

[[ 3 -5  6]
 [ 7 -1  0]
 [-5  9  4]
 [ 3 -5  1]]

We can use the following code to replace all negative values with zero in the NumPy array:

#replace all negative values with zero in 2D array
my_array[my_array <0] = 0#view updated array
print(my_array)

[[3 0 6]
 [7 0 0]
 [0 9 4]
 [3 0 1]]

Notice that all negative values in the original 2D array have been replaced with zero.

The following tutorials explain how to perform other common tasks in NumPy: