Inheritance problem?

[KraftDiner]

I have a class

class MyClass(MyBaseC lass)
def __init__(self)
super(self.__cl ass__, self).__init__( )
self.type = MyClassType
return self

It has a few methods...
I have another class and the only difference is the __init__ method..

I tried this:
class MySpecialClass( MyClass)
def __init__(self)
super(self.__cl ass__, self).__init__( )
self.type = MySpecialClassT ype # This is the only line
that's different between the two classes.
return self

At runtime I get an error:
RuntimeError: maximum recursion depth exceeded
What have I done wrong?

[Simon Percivall]

Re: Inheritance problem?

Don't use self.__class__, use the name of the class.

[Pierre Barbier de Reuille]

Re: Inheritance problem?

Well, I would even add : don't use super !
Just call the superclass method :

MyClass.__init_ _(self)



Simon Percivall a écrit :[color=blue]
> Don't use self.__class__, use the name of the class.
>[/color]

[Xavier Morel]

Re: Inheritance problem?

Pierre Barbier de Reuille wrote:[color=blue]
> Well, I would even add : don't use super !
> Just call the superclass method :
>
> MyClass.__init_ _(self)
>
>
>
> Simon Percivall a écrit :[color=green]
>> Don't use self.__class__, use the name of the class.
>>[/color][/color]
Bad idea if you're using new-style classes with a complex inheritance
hierarchy and multiple inheritance.

[Pierre Barbier de Reuille]

Re: Inheritance problem?

Xavier Morel a écrit :[color=blue]
> Pierre Barbier de Reuille wrote:
>[color=green]
>> Well, I would even add : don't use super !
>> Just call the superclass method :
>>
>> MyClass.__init_ _(self)
>>
>>
>>
>> Simon Percivall a écrit :
>>[color=darkred]
>>> Don't use self.__class__, use the name of the class.
>>>[/color][/color]
> Bad idea if you're using new-style classes with a complex inheritance
> hierarchy and multiple inheritance.[/color]

As a reference :

http://fuhm.org/super-harmful/

I may say this is the only place I ever saw what "super" *really* is
for. The behavior is far too complex and misthought. All I can say is :
don't use it ! It solves *nothing* and creates too many bugs in the long
run.

[Xavier Morel]

Re: Inheritance problem?

Pierre Barbier de Reuille wrote:[color=blue]
> Xavier Morel a écrit :[color=green]
>> Pierre Barbier de Reuille wrote:
>>[color=darkred]
>>> Well, I would even add : don't use super !
>>> Just call the superclass method :
>>>
>>> MyClass.__init_ _(self)
>>>
>>>
>>>
>>> Simon Percivall a écrit :
>>>
>>>> Don't use self.__class__, use the name of the class.
>>>>[/color]
>> Bad idea if you're using new-style classes with a complex inheritance
>> hierarchy and multiple inheritance.[/color]
>
> As a reference :
>
> http://fuhm.org/super-harmful/
>
> I may say this is the only place I ever saw what "super" *really* is
> for. The behavior is far too complex and misthought. All I can say is :
> don't use it ! It solves *nothing* and creates too many bugs in the long
> run.[/color]

My own encounter with the subject was Guido's "Unifying types and
classes in Python 2.2" (http://www.python.org/2.2.3/descrintro.html#mro
for the part on super itself), but I'll keep your link close by.

[Mike Meyer]

Re: Inheritance problem?

Xavier Morel <xavier.morel@m asklinn.net> writes:[color=blue]
> Pierre Barbier de Reuille wrote:[color=green]
>> Well, I would even add : don't use super !
>> Just call the superclass method :
>> MyClass.__init_ _(self)
>> Simon Percivall a écrit :[color=darkred]
>>> Don't use self.__class__, use the name of the class.[/color][/color]
> Bad idea if you're using new-style classes with a complex inheritance
> hierarchy and multiple inheritance.[/color]

To quote the original code:

class MyClass(MyBaseC lass)
def __init__(self)
super(self.__cl ass__, self).__init__( )
self.type = MyClassType
return self

class MySpecialClass( MyClass)
def __init__(self)
super(self.__cl ass__, self).__init__( )
self.type = MySpecialClassT ype
return self

The only place it uses self.__class__ is in the calls to super. Super
finds the superclass of it's first argument. If that argument is
self.__class__, then super will always return the superclass of the
class of self, *not* the superclass of the class who's code is being
run. That's why the code resuls in an infinite recursion.

And a note to the OP: __init__'s return value is ignored. You should
delete the "return self" from your methods.

<mike
--
Mike Meyer <mwm@mired.or g> http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.

[KraftDiner]

Re: Inheritance problem?

So ok I've written a piece of code that demonstrates the problem.
Can you suggest how I change the Square class init?

class Shape(object):
def __init__(self):
print 'MyBaseClass __init__'

class Rectangle(Shape ):
def __init__(self):
super(self.__cl ass__, self).__init__( )
self.type = Rectangle
print 'Rectangle'

class Square(Rectangl e):
def __init__(self):
super(self.__cl ass__, self).__init__( )
self.type = Square
print 'Square'

r = Rectangle()
s = Square()

[Pierre Barbier de Reuille]

Re: Inheritance problem?

KraftDiner a écrit :[color=blue]
> So ok I've written a piece of code that demonstrates the problem.
> Can you suggest how I change the Square class init?
>
> class Shape(object):
> def __init__(self):
> print 'MyBaseClass __init__'
>
> class Rectangle(Shape ):
> def __init__(self):
> super(self.__cl ass__, self).__init__( )
> self.type = Rectangle
> print 'Rectangle'
>
> class Square(Rectangl e):
> def __init__(self):
> super(self.__cl ass__, self).__init__( )
> self.type = Square
> print 'Square'
>
> r = Rectangle()
> s = Square()
>[/color]

I suggest you have a look at the link I gave before :

http://fuhm.org/super-harmful/

It gives a good explanation about what happens with "super".

At least, if you *really* want to use it, change your code like that :

class Shape(object):
def __init__(self):
super(Shape, self).__init__( )
print 'Shape __init__'

class Rectangle(Shape ):
def __init__(self):
super(Rectangle , self).__init__( )
self.type = Rectangle
print 'Rectangle'

class Square(Rectangl e):
def __init__(self):
super(Square, self).__init__( )
self.type = Square
print "Square"

r = Rectangle()
s = Square()


But, once more, I would recommand to use direct method call ....

Pierre

[Scott David Daniels]

Re: Inheritance problem?

KraftDiner wrote:[color=blue]
> So ok I've written a piece of code that demonstrates the problem.
> Can you suggest how I change the Square class init?
>
> class Shape(object):
> def __init__(self):
> print 'MyBaseClass __init__'
>
> class Rectangle(Shape ):
> def __init__(self):
> # super(self.__cl ass__, self).__init__( )[/color]
super(Rectangle , self).__init__( ) # XXX fixed[color=blue]
> self.type = Rectangle
> print 'Rectangle'
>
> class Square(Rectangl e):
> def __init__(self):
> # super(self.__cl ass__, self).__init__( )[/color]
super(Square, self).__init__( ) # XXX fixed[color=blue]
> self.type = Square
> print 'Square'
>
> r = Rectangle()
> s = Square()
>[/color]


--
-Scott David Daniels
scott.daniels@a cm.org