Python error?

import math
import numexpr as ne
import matplotlib.pyplot as plt
import numpy as np
import numba as nb
M = 10
A = 10
D = 0.1
xmin = -4
xmax = 4
n = 800
tfinal = 3
tinicial = 1
# GENERANDO VECTOR CON PUNTOS DE DISCRETIZACION X ESPACIADOS
x= np.linspace(xmin, xmax, n)
#GENERANDO FUNCION ANALITICA
def Cdifuana(M,A,D,x,t):
    temp = A*math.sqrt(4*math.pi*D*t);
    Cdifuana = (M/temp)*math.exp(-x**2 /(4*D*t))
#GENERANDO CONDICION INICIAL
C=(Cdifuana(M,A,D,x,tinicial))