"""

Singleton Pattern - Simplest pattern of all that ensures only one class

has only one instance and it is a global property.

Example - Usually for configuration settings where you don't want to create

a chaos by having many instances of the same class

The example below referenced from Python's documentation:

https://www.python.org/download/releases/2.2/descrintro/#__new__

"""

class Singleton(object):

def __new__(cls, *args, **kwds):

it = cls.__dict__.get("__it__")

if it is not None:

return it

cls.__it__ = it = object.__new__(cls)

it.init(*args, **kwds)

return it

def init(self, *args, **kwds):

pass

class ConfigModule(Singleton):

def someReallyUsefulFunction(self):

print "Hello World"

instance1 = ConfigModule()

instance2 = ConfigModule()

assert instance1 is instance2