[Python-Dev] Breaking calls to object.init/new (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Thu Mar 22 04:45:24 CET 2007

Jean-Paul Calderone wrote:

Perhaps I misunderstand the patch, but it would appear to break not just some inadvisable uses of super(), but an actual core feature of super(). Maybe someone can set me right. Is this correct?

class Base(object): def init(self, important): If so, what are the implications for this? class Other(object): def init(self, important):

I think the idea was that each init method extracts the arguments that apply to it and doesn't pass them on. Then, by the time object.init is reached, there should be none left.

This only works if the sets of keywords recognised by each init method are all disjoint.

Another approach is for none of them to extract anything, and always pass everything on. Then you need something at the top that accepts anything, and you get no error checking.

This kind of thing seems to be a general feature of super, i.e. in order for it to work properly, all the classes using it have to agree on some set of rules or other. This creates isolated ghettos of classes that can't be mixed with each other. If you try to mix in a class which doesn't know about the rules, or follows a different set of rules, everything falls apart.

Every time I've considered using super, I've eventually decided against it for reasons like this. I've always found a better way that doesn't introduce so may strange interactions between the classes involved.

-- Greg Ewing, Computer Science Dept, +--------------------------------------+ University of Canterbury, | Carpe post meridiem! | Christchurch, New Zealand | (I'm not a morning person.) | greg.ewing at canterbury.ac.nz +--------------------------------------+

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