numpy.ndarray is not a callable

Question

def sigmoid(x):

    s = 1/(1+np.exp(-x))  
    return s  



def sigmoid_derivative(x):

     #Arguments: x is A scalar or numpy array


    s = sigmoid(x)
    ds = s(1-s)

    return ds

x = np.array([1, 2, 3])
print ("sigmoid_derivative(x) = " + str(sigmoid_derivative(x)))

I get this error:

  TypeError  :                              Traceback (most recent call 
 last)
  <ipython-input-66-2715e4ef84dc> in <module>()
        1 x = np.array([1, 2, 3])
  ----> 2 print ("sigmoid_derivative(x) = " + str(sigmoid_derivative(x)))

  <ipython-input-65-177c1f00eabb> in sigmoid_derivative(x)
        16     s = sigmoid(x)
    ---> 17     ds = s(1-s)


   TypeError: 'numpy.ndarray' object is not callable

I don't understand where I am going wrong in this. I tried changing it to np.exp() but it still doesn't work. I have been trying to read the documentation and still no clue as to what needs to be done. Can someone give me some pointers?

Answer 1

the problem is s(1-s) , in python using () is to call a function(a callable). for multi, you should put * there. change your line of code to:

ds = s*(1-s)