handle exception divide by zero

[behnazpp]

Hi
thanks for your nice code. in my series I have meny zeros. how to handle that when I want to calc error rate?
def __forecast_value(self, x1, a_value, b_value, k):
---> 21 return (1 - math.exp(a_value)) * (x1 - (b_value / a_value)) * math.exp(-a_value * k)
22
23 def __forecast(self, patterns, period=1):

ZeroDivisionError: float division by zero

I tried to shift the numbers and now the series dont have any zeros.
still exception below occure. do you know why?

ZeroDivisionError: float division by zero