method_1_singleton.py

class SingleTon: 
  # Creating a static private variable
  _instance = None 
  # __new__ is called inside __init__ for object instantiation. 
  def __new__(self): 
    if( not self._instance ): 
      self._instance = super(SingleTon, self).__new__(self) 
      self.y = 10 
    return self._instance 

obj1 = SingleTon()
print(obj1.y)
obj1.y = 30
obj2 = SingleTon()
print(obj2.y)