CODEWITHSUNDEEP
pythonpython-3.x
Kwantuum
Kwantuum

Reputation: 163

What is the cleanest way of setting default values for attributes unless provided by the class call?

Currently this is what I'm doing:

class NewShip:
    def __init__(self, position = (0,0), x_velocity = 25, y_velocity = 15, anim_frame = 1, frame1 = "space_ship_1.png", frame2 = "space_ship_2.png", angle = 0, border_size = 900):
        self.position = position
        self.angle = angle
        self.x_velocity = x_velocity #in pixels per frame
        self.y_velocity = y_velocity #in pixels per frame
        self.anim_frame = anim_frame
        self.frame1 = pygame.image.load(frame1).convert_alpha()
        self.frame2 = pygame.image.load(frame2).convert_alpha()
        self.frame1 = pygame.transform.scale(self.frame1, (128,128))
        self.frame2 = pygame.transform.scale(self.frame2, (128,128))
        self.position = DummyObject()
        self.position.x = position[0]
        self.position.y = position[1]
        self.border_size = border_size

but honestly that's quite tedious and makes adding any more facultative attributes a real pain.

Should I just skip the whole 'letting people declare attributes with keyword arguments' thing and just instantiate objects in a fully default state before changing any of their attributes?

EDIT: apparently this works perfectly:

class NewShip:
    def __init__(self, **kwargs):
        self.angle = 0
        self.x_velocity = 25 #in pixels per frame
        self.y_velocity = 15 #in pixels per frame
        self.anim_frame = 1
        frame1 = "space_ship_1.png"
        frame2 = "space_ship_2.png"
        self.position = DummyObject()
        self.position.x = 0
        self.position.y = 0
        self.border_size = 900
        for element in kwargs: setattr(self, element, kwargs[element])
        self.frame1 = pygame.image.load(frame1).convert_alpha()
        self.frame2 = pygame.image.load(frame2).convert_alpha()
        self.frame1 = pygame.transform.scale(self.frame1, (128,128))
        self.frame2 = pygame.transform.scale(self.frame2, (128,128))

that is, just setting all defaults values then overriding them with the keyword args using for element in kwargs: setattr(self, element, kwargs[element])

Let me know if there's any cleaner way, though I have to say I'm much more satisfied with this.

Upvotes: 2

Views: 68

Answers (1)

Dimitris Fasarakis Hilliard
Dimitris Fasarakis Hilliard

Reputation: 160377

To reduce the clutter, you could alternatively define a defaults dictionary attribute _init_attrs for example, define your function with **kwargs and then setattr on self with a loop, using _init_attrs[k] as a default value for kwargs.get when no parameters were supplied:

class NewShip:
    def __init__(self, **kwargs):
        _init_attrs = {'angle': 0,
             'anim_frame': 1,
             'border_size': 900,
             'frame1': 'space_ship_1.png',
             'frame2': 'space_ship_2.png',
             'position': (0, 0),
             'x_velocity': 25,
             'y_velocity': 15 }

        for k, v in _init_attrs.items():
            setattr(self, k, kwargs.get(k, v)

This makes __init__ a bit more mystifying but achieves the goal of making it way more extensible while cutting down the size.

Upvotes: 3

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