Recursion problem

[Dennis Peterson]

I'm trying to implement a basic Composite pattern. In the following code, I
expect c.getData() and d.getData() to both return "hellogoodbye". Instead,
on d.getData() I get stacktrace printing "y += i.getData()" repeatedly until
recursion depth exceeded. Why?

I'm new to Python, running latest Windows version just downloaded.

class Simple:
    def __init__(self,x):
        self.data = x
    def getData(self):
        return self.data

class Compound:
    data = []
    def getData(self):
        y = ""
        for i in self.data:
            y += i.getData()
        return y

def test():
    a = Simple("hello")
    b = Simple("goodbye")
    c = Compound()
    c.data.append(a)
    c.data.append(b)
    print c.getData()
    d = Compound()
    d.data.append(c)
    print d.getData()