Inheritance problem?

[KraftDiner]

I have a class

class MyClass(MyBaseClass)
def __init__(self)
super(self.__class__, 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.__class__, self).__init__()
self.type = MySpecialClassType # 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]

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

 

[Pierre Barbier de Reuille]

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

MyClass.__init__(self)



Simon Percivall a écrit :

 

[Xavier Morel]

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

MyClass.__init__(self)



Simon Percivall a écrit :

Bad idea if you're using new-style classes with a complex inheritance
hierarchy and multiple inheritance.

 

[Pierre Barbier de Reuille]

Xavier Morel a écrit :

Bad idea if you're using new-style classes with a complex inheritance
hierarchy and multiple inheritance.

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]

Xavier Morel a écrit :

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.

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]

Bad idea if you're using new-style classes with a complex inheritance
hierarchy and multiple inheritance.

To quote the original code:

class MyClass(MyBaseClass)
def __init__(self)
super(self.__class__, self).__init__()
self.type = MyClassType
return self

class MySpecialClass(MyClass)
def __init__(self)
super(self.__class__, self).__init__()
self.type = MySpecialClassType
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

 

[KraftDiner]

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.__class__, self).__init__()
self.type = Rectangle
print 'Rectangle'

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

r = Rectangle()
s = Square()

 

[Pierre Barbier de Reuille]

KraftDiner a écrit :

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.__class__, self).__init__()
self.type = Rectangle
print 'Rectangle'

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

r = Rectangle()
s = Square()

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(Rectangle):
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]

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.__class__, self).__init__()

super(Rectangle, self).__init__() # XXX fixed

self.type = Rectangle
print 'Rectangle'

class Square(Rectangle):
def __init__(self):
# super(self.__class__, self).__init__()

super(Square, self).__init__() # XXX fixed