unsupported operand type(s) for -: 'numpy.str_' and 'numpy.str_'

This error occurs when you try to perform a subtraction operation (-) between two numpy string objects. Numpy string objects are not numerical, and therefore cannot be subtracted from each other.

To fix this error, you need to make sure that the objects you are trying to subtract are numerical. You can convert numpy string objects to numerical data types using functions like int() or float().

For example, if you have two numpy string objects '10' and '5', you can convert them to integers and subtract them as follows:

a = '10'
b = '5'
result = int(a) - int(b)
print(result)

This will output: 5

Alternatively, you can also use the numpy function np.subtract() to perform element-wise subtraction between two numpy arrays.

import numpy as np

a = np.array(['10', '20', '30'])
b = np.array(['5', '10', '15'])

result = np.subtract(a.astype(int), b.astype(int))
print(result)

This will output: [ 5 10 15]