initialization - Why Singleton in python calls __init__ multiple times and how to avoid it? -

i've implementation of singleton pattern in python, i've noticed init called, uselessly, everytime call myclass, despite same instance returned.

how can avoid it?

class test(object):     def __init__(self, *args, **kwargs):         object.__init__(self, *args, **kwargs)  class singleton(object):   _instance = none    def __new__(cls):     if not isinstance(cls._instance, cls):         cls._instance = object.__new__(cls)     return cls._instance  class myclass(singleton):     def __init__(self):         print("should printed 1 time")         self.x=test()         pass  = myclass() # prints: "should printed 1 time" b = myclass() # prints ( again ): "should printed 1 time"  print(a,b) # prints: 0x7ffca6ccbcf8 0x7ffca6ccbcf8 print(a.x,b.x) # prints: 0x7ffca6ccba90 0x7ffca6ccba90 

the problem __new__ doesn't return object, returns unitialized object on __init__ called afterwards.

you can't avoid @ all. can following(using metatypes):

class singleton(type):     def __init__(self, name, bases, mmbs):         super(singleton, self).__init__(name, bases, mmbs)         self._instance = super(singleton, self).__call__()      def __call__(self, *args, **kw):         return self._instance  class test(metaclass = singleton):     # __metaclass__ = singleton # in python 2.7     def __init__(self, *args, **kw):         print("only ever called once")