single_execution_property.py

class SomeClass:
    class single_execution:
        """Compute property only once and cache the result for further access.
        When the property is first accessed, the result is computed, and the
        attribute on the instance is replaced with the result. This is
        essentially a single execution lazy property.
        """
        def __init__(self, method):
            self.__method = method
            self.__attribute_name = method.__name__

        def __get__(self, instance, owner):
            result = self.__method(instance)
            setattr(instance, self.__attribute_name, result)
            return result
          
    @single_execution
    def foo(self):
        return "some super expensive operation"