Below is a snippet where I have lengthy calculation which I only want to perform once - because it takes a long time. I need to call this calculation repeatedly in other methods (in this example, only one - do_something_with_my_value).
Is there a way I can make my_value execute only once, and store the value down for the purposes of using it in do_something_with_my_value?
I could bind the return value of my_value in the function itself by manually setting a class attribute. But this would require the type hint to return None.
from typing import List
class Example:
def __init__(self) -> None:
pass
def my_value(self) -> int:
"""Lenghthy calcultion, and so don't want to put in __init__"""
return 1
def do_something_with_my_value(self) -> List[int]:
"""Repeatedly uses my_value."""
return [x + self.my_value() for x in range(1, 1000)]
I'm wondering if there's a "pythonic" design that avoid repeatedly doing a lengthy calculation as in the snippet above.
Many thanks for your help.
If my_value never changes throughout the life-cycle of your class then the functools.cached_property decorator is ideal:
from functools import cached_property
class Example:
@cached_property
def my_value(self) -> int:
"""Lengthy calculation goes here"""
return 1
def do_something_with_my_value(self) -> list[int]:
"""Note how my_value is accessed as a property rather than a function call"""
return [x + self.my_value for x in range(1, 1000)]