The result will be different from the result you should have.Please tell me about "nan".

import numpy as np
import matplotlib.pyplot asplt

def3(x0,x1):
    r=2*x0**2+x1**2
    an=r*np.exp(-r)
    returnans# Add this line

xn = 9
x0 = np.linspace (-2,2,xn)
x1 = np.linspace (-2,2,xn)
y=np.zeros(len(x0),len(x1))))
for i0 in range (xn):
    for i1 in range (xn):
      y[i1, i0] = f3 (x0[i0], x1[i1])

print(x0)
print(np.round(y,1))