[Tutor] Superclass call problem

[Alan Harris-Reid]

>> Hi,
>>
>> I am having trouble understanding how superclass calls work.  Here's
>> some code...
>>     
>
> What version of Python are you using?
>
> In Python 2.x, you MUST inherit from object to use super, and you MUST 
> explicitly pass the class and self:
>
> class ParentClass(object):
>     def __init__(self, a, b, c):
>         do something here
>
> class ChildClass(ParentClass):
>     def __init__(self, a, b, c):
>         super(ChildClass, self).__init__(a, b, c)
>
> In Python 3.x, all classes inherit from object and you no longer need to 
> explicitly say so, and super becomes a bit smarter about where it is 
> called from:
>
> # Python 3 only
> class ParentClass:
>     def __init__(self, a, b, c):
>         do something here
>
> class ChildClass(ParentClass):
>     def __init__(self, a, b, c):
>         super().__init__(a, b, c)
>
>
> I assume you are using Python 3.0 or 3.1. (If you're 3.0, you should 
> upgrade to 3.1: 3.0 is s-l-o-w and no longer supported.)
>
>
> Your mistake was to pass self as an explicit argument to __init__. This 
> is not needed, because Python methods automatically get passed self:
>
>   
>>     def __init__(self):
>>         super().__init__(self)
>>     
>
> That has the effect of passing self *twice*, when __init__ expects to 
> get self *once*, hence the error message you see:
>
>   
>> When the super().__init__ line runs I get the error "__init__() takes
>> exactly 1 positional argument (2 given)"
>>     
Hi Steven, thanks for the reply.

Fortunately I am using Python 3.1, so I can use the super().__init__(a, 
b, c) syntax.

Regards,
Alan
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