How to optimize a frequently read method in a python class?

Question

There are many methods defined in MyClass that needs to call read_my_obj, is the code below a good way to avoid re-creating a new MyObjectType instance every time to save memory and improve execution speed? Or is there a more pythonic way to do achieve this type of pattern?

class MyClass:
  my_obj: Optional[MyObjectType] = None
  
  @classmethod
  def read_my_obj(cls) -> MyObjectType:
     if cls.my_obj is not None:
         return cls.my_obj  # treating my_obj as a singleton, to avoid instantiating a new one each time
     obj_field = read_from_db()
     cls.my_obj = MyObjectType(obj_field)  # instantiate my object for first time
     return cls.my_obj

Asked By: user1008636

||

Source

Answer 1

I would use a hidden attribute + property to achieve "run-time" caching of instantiated objects:

class MyClass:
    def __init__(self):
        self._my_obj = None  # hidden attribute begins with an underscore
 
    @property
    def my_obj(self): -> MyObjectType
        # Create if not exists
        if not self._my_obj:
            obj_field = read_from_db()
            self._my_obj = MyObjectType(obj_field)
        # return hidden attribute
        return self._my_obj

Do note that this hidden attribute will only get populated once per class instance (on accessing property). If you need more frequent refreshes, you could configure some datetime logic within the property.

Answered By: Yaakov Bressler

How to optimize a frequently read method in a python class?

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