Hello everyone.
I'm trying to understand how to use the two methods. I know that __new__ is
used to create an object, while __init__ to initialize. But I'm not sure
what happens when I create an object.
I found the following code in the book (Python 3 Object Oriented
Programming by Dusty Phillips)
import weakref
class CarModel:
_models = weakref.WeakValueDictionary()
def __new__(cls, model_name, *args, **kwargs):
model = cls._models.get(model_name)
if not model:
model = super().__new__(cls)
cls._models[model_name] = model
return model
def __init__(self, model_name, air = False, tilt = False, cruise_control
= False, power_locks = False, alloy_wheels = False, usb_charger = False):
if not hasattr(self, "initted"):
self.model_name = model_name
self.air = air
self.tilt = tilt
self.cruise_control = cruise_control
self.power_locks = power_locks
self.alloy_wheels = alloy_wheels
self.usb_charger = usb_charger
self.intted = True
dx = CarModel("Fit DX")
lx = CarModel("Fit LX", air = True, tilt = True, cruise_control = True,
power_locks = True, alloy_wheels = True, usb_charger = True)
I assume when I call CarModel(<parameters>) __new__is being called first
and then __init__ after it.
1) Does it mean that __new__ and __init__ must have the same parameters? In
this particular case __new__ and __init__ both have model_name and if I
understand correctly when __new__ is called the rest of the parameters
(air, tilt, cruise_control, etc) are absorbed by the *args argument. Please
correct me if I am wrong.
2) What happens if I don't use the same parameters, say in the case of
__init__ I will remove model_name, will I still be able to call dx =
CarModel("Fix DX")
I realize questions might seem a bit strange or simplistic but I just want
to make sure I have a correct understanding of things.
Any help is appreciated.
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