Instantiate parent class only once when calling from two child classes

Question

I would like to know if there's a way that we can instantiate a class only once when called from one of the child class and somehow cache it and use it for second child class without instantiating the parent class.

class A:
   def __init__(self):
      #some huge data stored in self parameters.
class B:
   def __init__(self):
      A.__init__(self)
class C:
   def __init__(self):
      A.__init(self)

So both classes B and C uses class A as a parent class and class A has huge data initialised which can be used by both classes B and C. So what I'm trying to achieve here is when I instantiate class B for example, it instantiates class A and loads all the data into memory and to cache the instance so when I immediately instantiate class C it looks for the existing instance of the class without instantiating it again.

Use singleton approach it ensures to create heavy objects only once and stores in memory as one object and whenever wants it just call it ,search for singleton in python — Ali Nour, Aug 20 '21 at 15:45
Does this answer your question? [Is there a simple, elegant way to define singletons?](https://stackoverflow.com/questions/31875/is-there-a-simple-elegant-way-to-define-singletons) or perhaps https://stackoverflow.com/questions/6760685/creating-a-singleton-in-python — JonSG, Aug 20 '21 at 15:49

ilpianoforte · Answer 1 · 2021-08-21T18:29:33.663

How about instantiating A in B and providing a method to transfer the data from B to outside? See below:


class A:
   def __init__(self):
      self.huge_data = [.....]

   def data(self):
      return self.huge_data

class B:
   def __init__(self):
      self.a = A()

   def pass_data(self)
      return a.data()

class C:
   def __init__(self):
      A.__init(self)

Once you instantiate B, you will be able to use the method to access the data.

Instantiate parent class only once when calling from two child classes

1 Answers1