copysort patch, was RE: [Python-Dev] inline sort option

[Guido van Rossum]

> Hmmm... maybe one COULD make a custom descriptor that does support
> both usages... and maybe it IS worth making the .sorted (or whatever name)
> entry a case of exactly such a subtle custom descriptor...

Thanks for the idea, I can use this as a perverted example in my talk
at Stanford tomorrow.  Here it is:

import new

def curry(f, x, cls=None):
    return new.instancemethod(f, x)

class MagicDescriptor(object):
    def __init__(self, classmeth, instmeth):
        self.classmeth = classmeth
        self.instmeth = instmeth
    def __get__(self, obj, cls):
        if obj is None:
            return curry(self.classmeth, cls)
        else:
            return curry(self.instmeth, obj)

class MagicList(list):
    def _classcopy(cls, lst):
        obj = cls(lst)
        obj.sort()
        return obj
    def _instcopy(self):
        obj = self.__class__(self)
        obj.sort()
        return obj
    sorted = MagicDescriptor(_classcopy, _instcopy)

class SubClass(MagicList):
    def __str__(self):
        return "SubClass(%s)" % str(list(self))

unsorted = (1, 10, 2)
print MagicList.sorted(unsorted)
print MagicList(unsorted).sorted()
print SubClass.sorted(unsorted)
print SubClass(unsorted).sorted()

--Guido van Rossum (home page: http://www.python.org/~guido/)