How to Fix FutureWarning: elementwise comparison failed; returning scalar, but in the future will perform elementwise comparison

FutureWarning: elementwise comparison failed; returning scalar, but in the future will perform elementwise comparison warning occurs when you “compare numpy array with another object obj using arr == obj.”

This warning is raised when you try to perform an elementwise comparison operation (like == or !=) between an array and an object of a different shape or type, and the comparison doesn’t behave as one might intuitively expect.

Flow diagram

Diagram of How to Fix FutureWarning: elementwise comparison failed; returning scalar, but in the future will perform elementwise comparison

Reproducing the warning

import numpy as np

np.arange(3) == np.arange(3).astype(str)

Output

FutureWarning: elementwise comparison failed; returning scalar instead, 
               but in the future will perform elementwise comparison

You can see that the warning you’re encountering is caused by attempting to compare two NumPy arrays with different data types. The first array (np.arange(3)) contains integers, while the second array (np.arange(3).astype(str)) has been cast to strings.

How to fix it

To fix the FutureWarning: elementwise comparison failed; returning scalar, but in the future will perform elementwise comparison, you can use the .astype() function to ensure that both arrays have the same data type before comparing.

Visual representation of Converting an array to a string

You can convert a numpy array’s data type using the .astype() function.

import numpy as np

arr_1 = np.arange(3).astype(str)
arr_2 = np.arange(3).astype(str)

print(arr_1 == arr_2)

Output

[ True True True]

That’s it!

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