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Python Object-Oriented Python Inheritance Multiple Superclasses

Hoessein Abd
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Hoessein Abd
Python Web Development Techdegree Graduate 19,107 Points
Posted by Hoessein Abd
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Hoessein Abd
Python Web Development Techdegree Graduate 19,107 Points

Why does an attribute from a superclass change when an instance is made from a subclass?

So at around 4.16 in this video Kenneth makes an instance of the Thief class and gives it a name and sets sneaky to False. When an instance is made the init method will run from the Thief class and that sneaky will be set to False. Why does print(hoessein.hide(8)) result in False? The sneaky is True in the Sneaky class and also True in the Sneaky's init method. 

from thieves import Thief

hoessein = Thief("Hoessein", sneaky=False)
print(hoessein.sneaky)
print(hoessein.agile)
print(hoessein.hide(8))

The output is:

False
True
False

I expected the sneaky only to be changed here when an instance is made from the thief's class:

import random

from attributes import Agile, Sneaky
from characters import Character

class Thief(Character, Agile, Sneaky):
    sneaky = True

    def __init__(self, name, sneaky=True, **kwargs):
        super().__init__(name, **kwargs)
        self.sneaky = sneaky

    def pickpocket(self):
        return self.sneaky and bool(random.randint(0, 1))

I didn't expect sneaky to change in the Sneaky class when I make an instance of the thief's class and set sneaky to false. Why does it do that? 

import random

class Sneaky:
    sneaky = True

    def __init__(self, sneaky=True, *args, **kwargs):
        super().__init__()
        self.sneaky = sneaky

    def hide(self, light_level):
        return self.sneaky and light_level < 10

1 Answer

Ryan S
Ryan S
27,276 Points
Ryan S
Ryan S
27,276 Points

Hi Hoessein,

The sneaky attribute only defaults to True in the Sneaky __init__ method if a value is not provided. In the example given, you have overwritten the default by providing sneaky=False, so self.sneaky will be False as a result.

Ryan S
Ryan S
27,276 Points
Ryan S
Ryan S
27,276 Points

The Thief class inherits from Sneaky, and it is in Sneaky's __init__ method where it is possible to override the sneaky attribute value. So when an instance of Thief is created, the sneaky=False value ultimately gets passed along to the Sneaky __init__ method, and will set the sneaky attribute for that instance of Thief.

You aren't directly changing the sneaky value of the Sneaky class, you are setting the sneaky value in the Thief instance, which is inherited from the Sneaky class.

Hoessein Abd
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Hoessein Abd
Python Web Development Techdegree Graduate 19,107 Points
Hoessein Abd
.a{fill-rule:evenodd;}techdegree seal-36
Hoessein Abd
Python Web Development Techdegree Graduate 19,107 Points

Ah, of course, i'm not changing the sneaky in the sneaky class, just the instance of the thieves class is sneaky. makes sense, thanks for the explanation.