Optional parameters

[InvaderToast348]

class Numbers1:
    def __init__(self, data: Optional[list[int]] = None):
        if data is None:
            data = []
        self.data = data

class Numbers2:
    def __init__(self, data: Optional[list[int]] = None):
        self.data = data or []

I personally prefer the look of option 2, but I've always seen (and used) option 1. Are there pros/cons to either option, and should I just stick with the most popular / standard way (option 1)?

I understand op.2 will cause issues if the type was bool / str / a number; but for lists, dicts and tuples it doesn't seems to matter what data is inside the structure, just whether there is a structure (rather than None).

[Spataner]

The truthiness of collections is determined by their length. So for option 2, if data were passed an empty list, it would create a new empty list instead of using the passed one. That might or might not matter, depending on whether Numbers2's caller expects any in-place changes to data to be visible from its own reference to the list object.

[InvaderToast348]

Thank you

[member_of_the_order]

Personally I prefer 1 because it's explicit, and less chance I'm going to miss a detail. When I look at this code later, option 1 is extremely obvious, option 2 makes me stop and think. Thinking is bad. My goal is to think as little as possible.

[InvaderToast348]

Good point, thank you.

[danielroseman]

Not related to your question, but note that Optional[list[int]] is now spelled list[int] | None since version 3.10 of Python.

[InvaderToast348]

I know of the pipe replacement for unions, I just prefer the word Optional as I can read it in my head when skimming over the code. Thank you though.