[from scipy.optimize import curve_fit
from numpy import array, sinc,where
from sympy import *
values_y = array([0,0,16,9,4, 1, 0, 1, 4 ,9 ,16,0,0])
values_x = array(range(len(values_y)))
def func1(y, a,b,c3,c2 ):
   return where((y>=c3) &  (y<=c2),a*(y-b)**2, 0)
arg=curve_fit(func1, values_x, values_y, p0= (1,4,0,7))
print (arg)
C:\Users\9: OptimizeWarning: Covariance of the parameters could not be estimated
  category=OptimizeWarning)
(array([0.15560438, 5.99930899, 0.        , 7.        ]), array([[inf, inf, inf, inf],
       [inf, inf, inf, inf],
       [inf, inf, inf, inf],
       [inf, inf, inf, inf]]))
Process finished with exit code 0]

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