Basic Boolean homework help

[StillAnotherDave]

A follow-up question on the same homework.

import numpy as np


a = input('what is the coefficient for a? ')
b = input('what is the coefficient for b? ')
c = input('what is the coefficient for c? ')

# calculate the discriminant
d = (b**2)-(4*a*c)

sol1 = (-b-np.sqrt(d))/(2*a)
sol2 = (-b+np.sqrt(d))/(2*a)

if d > 0.:
    print('There are two real roots which are ', sol1, 'and', sol2)
elif d == 0.:
    print('There is one real root which is ', sol1)
else:
    print ('There are no real roots ')
    
    

Why does this not work??