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Start your free trialSon-Hai Nguyen
2,481 PointsEr.. why Kenneth changed the Character class to the last one called?
When class Thief(Character, Sneaky, Agile):
still worked just fine, why Kenneth changed the Character class to the last one called in class Thief(Sneaky, Agile, Character):
? I understand he's trying to demo us a case where error may occur, but in reality is there any case we will need to do that? What's the point behind doing that?
Thanks guys!!!
4 Answers
Chris Freeman
Treehouse Moderator 68,427 PointsGood Question. The specific difference between the parent class Character
and the other Agile
and Sneaky
classes is that the Character.__init__
does not have a call to super()
while the other two do have a super()
call. With Character
as the first parent class, the Agile.__init__
and Sneaky.__init__
will never be executed. By moving Character
to the last position, the super()
in Agile.__init__
can call Sneaky.__init__
which calls Character.__init__
.
In the example, code it still works with Character
as the first parent because it runs a loop to add all keyword arguments as attributes, such that self.agile
and self.sneaky
will get set regardless if the other __init__
methods are run. Where this would break, is if the other __init__
methods contained additional code beyond simple attribute assignment such as other attribute initialization that isn't defined by a keyword argument.
Post back if you need more help. Good luck!!
Son-Hai Nguyen
2,481 PointsThank you so much Chris!!!
Myles Brathwaite
1,971 PointsThank you Son for asking these questions honestly so helpful
Son-Hai Nguyen
2,481 PointsHi Chris. Thank you so much for your explanation. So basically Python will take all Sneaky
, Agile
and Character
as parents of Thief
class? Are they considered equally?
One more thing, so what does the super()
do in class Agile
and Sneaky
? As I understand, the super()
will inherit from the parent, but what are parents of Agile
and Sneaky
in this case, when class Sneaky:
and class Agile:
when there's no parentheses comes with them?
Thank you so much for your support Chris!!!
Chris Freeman
Treehouse Moderator 68,427 PointsGiven multiple base classes, they are considered in the order presented. Each object reference is first search for within Thief
instance, then the 'Thief` class, then in each of the base classes until a match is found. This is called the Method Resolution Order (MRO). The MRO can be seen:
- of an class:
classname.__mro__
- of an instance
instance.__class__.__mro__
Son-Hai Nguyen
2,481 PointsThank you so much Chris. And can you please tell me what does the super()
function do in class Sneaky:
and class Agile:
?
Thank you again Chris!!!
Chris Freeman
Treehouse Moderator 68,427 Pointssuper()
calls the method of the same name that is in the next base class along the MRO.
Son-Hai Nguyen
2,481 PointsSon-Hai Nguyen
2,481 PointsHi Chris,
Thank you so much for your reply. I see it much clearer now. But there's one thing I'm still left wondering, that is it true that the first class called is the parent class? Is it always setup this way?
Thank you again, Chris!!!
Chris Freeman
Treehouse Moderator 68,427 PointsChris Freeman
Treehouse Moderator 68,427 PointsCharacter
,Thief
, andSneaky
would all considered parent classes. The use of βparentβ and βchildβ comes from other languages. In Python, when describing inhertance and multiple inheritance, there are more precise terms. The classes listed within the parentheses of the class declaration are called base classes and the class being defined is call the derived classPost back if you need more help. Good luck!!!
Chris Freeman
Treehouse Moderator 68,427 PointsChris Freeman
Treehouse Moderator 68,427 PointsI should add the terminology class and subclass is also used. A given
DerivedClass
is also a subclass of eachBaseClass
listed in the signature line.