How to Replace Elements in NumPy Array (3 Examples)


You can use the following methods to replace elements in a NumPy array:

Method 1: Replace Elements Equal to Some Value

#replace all elements equal to 8 with a new value of 20
my_array[my_array == 8] = 20

Method 2: Replace Elements Based on One Condition

#replace all elements greater than 8 with a new value of 20
my_array[my_array > 8] = 20

Method 3: Replace Elements Based on Multiple Conditions

#replace all elements greater than 8 or less than 6 with a new value of 20
my_array[(my_array > 8) | (my_array < 6)] = 20

The following examples show how to use each method in practice with the following NumPy array:

import numpy as np

#create array
my_array = np.array([4, 5, 5, 7, 8, 8, 9, 12])

#view array
print(my_array)

[ 4  5  5  7  8  8  9 12]

Method 1: Replace Elements Equal to Some Value

The following code shows how to replace all elements in the NumPy array equal to 8 with a new value of 20:

#replace all elements equal to 8 with 20
my_array[my_array == 8] = 20

#view updated array
print(my_array)

[ 4  5  5  7 20 20  9 12]

Method 2: Replace Elements Based on One Condition

The following code shows how to replace all elements in the NumPy array greater than 8 with a new value of 20:

#replace all elements greater than 8 with 20
my_array[my_array > 8] = 20

#view updated array
print(my_array)

[ 4  5  5  7  8  8 20 20]

Method 3: Replace Elements Based on Multiple Conditions

The following code shows how to replace all elements in the NumPy array greater than 8 or less than 6 with a new value of 20:

#replace all elements greater than 8 or less than 6 with a new value of 20
my_array[(my_array > 8) | (my_array < 6)] = 20

#view updated array
print(my_array)

[20 20 20  7  8  8 20 20]

Additional Resources

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

How to Calculate the Mode of NumPy Array
How to Find Index of Value in NumPy Array
How to Map a Function Over a NumPy Array

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