Pfmsoft Aiohttp-Queue Utilities

pfmsoft.aiohttp_queue.utilities.optional_object(argument, object_factory, *args, **kwargs)

A convenience method for initializing optional arguments.

Meant to be used when solving the problem of passing an optional object where the desired behavior is a new object if None is passed. The problems with this are better explained here: https://docs.python-guide.org/writing/gotchas/#mutable-default-arguments

The standard solution is to use Optional[List] = None, check for None in your code, and initialize a new mutable as needed. optional_object saves a few line of code.

For example:

class SomeObject:
    data_1: int
    data_2: str


class MyClass:
    def __init__(
        self,
        plain_arg: int,
        with_data: Optional[List[str]] = None,
        new_dict: Optional[Dict[str, int]] = None,
        my_class: Optional[SomeObject] = None,
    ):
        default_some_object = {"data_1": 1, "data_2": "two"}
        self.plain_arg = plain_arg
        self.with_data: List[str] = optional_object(with_data, list, ["a", "b", "c"])
        self.new_dict: Dict[str, int] = optional_object(new_dict, dict)
        self.my_class: SomeObject = optional_object(
            my_class, SomeObject, **default_some_object
        )

Parameters

• argument (Optional[~T]) – An argument that is an object that may be None.

• object_factory (Callable[…, ~T]) – Factory function used to create the object.

• *args – Optional arguments passed to factory function.

• **kwargs – Optional keyword arguments passed to factory function.

Return type

~T

Returns

The initialized object.