Python AttributeError: property cannot overwrite inherited attribute?

Question

I still don't fully understand when and how to use properties. Here I have a class SpecialCar which is inheriting Car. The variable summer_tire should basically be equivalent to tire, except for the name. So whenever I am asking for either of those two, I want to get summer_tire.

Using @property results in an error. Deleting the @property line will print 0, but I want to get 2.

class Car():
    def __init__(self):
        self.tire = 0

class SpecialCar(Car):
    def __init__(self):
        Car.__init__(self)
        self.summer_tire = 2
        self.winter_tire = 5

    @property
    def tire(self):
        return self.summer_tire

i = SpecialCar()
print(i.tire)

Not an answer, but worth asking, if the property isn't computed why is it not a "real" property? — Reut Sharabani
– Reut Sharabani, Commented Feb 2, 2015 at 16:28

Martijn Pieters · Accepted Answer · 2015-02-02 16:36:32Z

4

You declared a property that doesn't have a setter, thus self.tire = 0 in Car.__init__ fails.

You could give your new property a setter:

class SpecialCar(Car):
    def __init__(self):
        Car.__init__(self)
        self.summer_tire = 2
        self.winter_tire = 5

    @property
    def tire(self):
        return self.summer_tire

    @tire.setter
    def tire(self, new_tire):
        self.summer_tire = new_tire

or you could avoid calling Car.__init__ altogether, or make Car.tire a class attribute, set as part of the class and replaced with the property in subclasses.

edited Feb 2, 2015 at 16:36

answered Feb 2, 2015 at 16:31

Martijn Pieters

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