Re: Subclass dynamically
Robert Dailey rcdai...@gmail.com (RD) wrote: RD Hey, RD I have a class that I want to have a different base class depending on RD a parameter that I pass to its __init__method. For example RD (pseudocode): RD class MyDerived( self.base ): RD def __init__( self, base ): RD self.base = base RD Something like that... and then I would do this: RD foo = MyDerived( MyBase() ) What do you want? As you write it now foo would be an instance of MyDerived, but you say you want to have a class with a different base class... So does this mean that foo should become that class or that foo should become an instance of a new anonymous class that has a specified base class? And on the other hand is MyBase the required base class. But you pass an instance of MyBase, not MyBase itself. As you have it above MyBase() should be a class, therefore MyBase should be a metaclass. Or is that not what you want? -- Piet van Oostrum p...@cs.uu.nl URL: http://pietvanoostrum.com [PGP 8DAE142BE17999C4] Private email: p...@vanoostrum.org -- http://mail.python.org/mailman/listinfo/python-list
Re: Subclass dynamically
On Sat, 08 Aug 2009 11:12:30 -0600, Robert Dailey rcdai...@gmail.com wrote: How can you subclass a class from an object?.. Hey, I have a class that I want to have a different base class depending on a parameter that I pass to its __init__method. For example (pseudocode): class MyDerived( self.base ): def __init__( self, base ): self.base = base Something like that... and then I would do this: foo = MyDerived( MyBase() ) Note I'm using Python 3.1 on Windows. Thanks in advance. -- Kind regards, Sergey Simonenko. -- http://mail.python.org/mailman/listinfo/python-list
Re: Subclass dynamically
Robert Dailey wrote: Hey, I have a class that I want to have a different base class depending on a parameter that I pass to its __init__method. For example (pseudocode): class MyDerived( self.base ): def __init__( self, base ): self.base = base Something like that... and then I would do this: foo = MyDerived( MyBase() ) Note I'm using Python 3.1 on Windows. Thanks in advance. Python makes it possible to change base classes, but that doesn't mean it ever a good idea. Moreover, the assignment is at the class level, not the instance level: MyDerived.__bases__ = (base,) #A tuple of bases would change the base class for the class MyDerived, and all instances past, present, or future. Better (but still not good) might be a factory function that derives a class with the desired base class: def Derive(base): class Derived(base): pass return Derived DerivedClass = Derive(MyBase) foo = DerivedClass(...) I believe that will produce what you were looking for. Gary Herron -- http://mail.python.org/mailman/listinfo/python-list
Re: Subclass dynamically
Quoting Robert Dailey rcdai...@gmail.com: Hey, I have a class that I want to have a different base class depending on a parameter that I pass to its __init__method. For example (pseudocode): 1- Are you sure that you want that behavior? Given that in python, a class is just a particular case of invocable object, you could just write a function instead, and the code may be more robust. 2- If you are /sure/ that is the behavior you want, take a look at the __new__ method. The __new__ can decide which instance to return (you could even define a new class inside of it, instantiate it, and return the instance). 3- You may want to take a look at metaclasses. But without more details about why you want it, I can't give you more precise answers. Regards, -- Luis Zarrabeitia Facultad de Matemática y Computación, UH http://profesores.matcom.uh.cu/~kyrie -- Participe en Universidad 2010, del 8 al 12 de febrero de 2010 La Habana, Cuba http://www.universidad2010.cu -- http://mail.python.org/mailman/listinfo/python-list
