Implement a function to find the greatest common divisor of two numbers in Python.
def gcd(a, b): 
    if(a == 0): 
        return b 
    if(b == 0): 
        return a 
  
    if(a == b): 
        return a 
  
    if(a > b): 
        return gcd(a-b, b) 
    return gcd(a, b-a)