singleton.py

class Singleton(type):
    _instances = {}

    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
        return cls._instances[cls]



"""
Use this by defining Singleton as a class' metaclass
"""

class Foo(object):
  __metaclass__ = Singleton
  
  """stuff"""