Singleton in Python

singleton.py

#!/usr/bin/env python

class Hello(object):
    singleton = None

    def __new__(clz):
        if not clz.singleton:
            clz.singleton = object.__new__(clz)
        return clz.singleton

    def __init__(self):
        self.world = "world"
        return None

h = Hello()
h.hello = "hello"

print h.hello
print h
print h.world

x = Hello()

print x.hello
print x
print x.world