Python (3.x) singleton metaclass. It allows manipulation of child classes, as well as converting all class funcs to classmethod's.

class_singleton.py

class ClassSingleton(type):
	def __new__(cls, cls_name, bases, attrs):
		for name, attr in attrs.items():
			if callable(attr):
				attrs[name] = classmethod(attr)
		return type.__new__(cls, cls_name, bases, attrs)
	
	def __init__(cls, cls_name, bases, attrs):
		cls.singleton()

sample_use.py

from class_singleton import ClassSingleton

class BaseClass(metaclass=ClassSingleton):
	attrs = {}

	def singleton(self):
		for attr in self.attrs.keys():
			#do some magic to attrs
			pass
    
class MyClass(BaseClass):
	attrs = {'some':'meaningful', 'attrs':'here'}
  
	def non_class_method(self, *args, **kwargs):
		#metaclass ClassSingleton would decorate this function (and all other funcs in this class) as classmethod.
		return {'attrs':self.attrs, 'args':args, 'kwargs':kwargs}