Recursive Function Call in OOP Python

So I've recently started doing Object Oriented Programming with Python, and for a specific problem I have to write a class that deals with fractions. Everything seems to be coming along fine with writing methods of common math operators s开发者_如何学Cuch as subtraction and addition; however, I am stuck with a recursive method.

class fractions():
    def __init__(self, numerator, denominator):
        self.numerator = numerator
        self.denominator = denominator
    def GreatestCommonDivisor(self, numerator, denominator): # This is the culprit
        if numerator%denominator == 0:
            return denominator
        else:
            return GreatestCommonDivisor(self, denominator, numerator%denominator)

When I call the Greatest Common Divisor function in another method that needs the to find the greatest divisor of the numerator, I get:

Traceback (most recent call last):
  File "C:\Program Files (x86)\Wing IDE 101 3.2\src\debug\tserver\_sandbox.py", line 1, in <module>
    # Used internally for debug sandbox under external interpreter
  File "C:\Program Files (x86)\Wing IDE 101 3.2\src\debug\tserver\_sandbox.py", line 9, in GreatestCommonDivisor
NameError: global name 'GreatestCommonDivisor' is not defined 

I call the function like this:

X = fractions(9, 36)
X.GreatestCommonDivisor(X.numerator, X.denominator)

If someone could tell me what the issue here is and how to fix it I would greatly appreciate it, this is my first usage of a recursive function in a class.

This line is where the NameError occurs:

return GreatestCommonDivisor(self, denominator, numerator%denominator)

It should read:

return self.GreatestCommonDivisor(denominator, numerator % denominator)

GreatestCommonDivisor is an instance method, not a global method. You need to do

return self.GreatestCommonDivisor(denominator, numerator%denominator)

But your code seems to show you don't really have object oriented concepts completely grasped yet.