On 3 November 2010 07:15, Robert Bradshaw <[email protected]>wrote:
> On Tue, Nov 2, 2010 at 10:59 PM, Stefan Behnel <[email protected]> > wrote: > > Robert Bradshaw, 02.11.2010 23:21: > >> On Tue, Nov 2, 2010 at 3:11 PM, Vitja Makarov wrote: > >>> http://docs.python.org/reference/datamodel.html#basic-customization > >>> > >>> """Called to create a new instance of class cls. __new__() is a static > >>> method (special-cased so you need not declare it as such) that takes > >>> the class of which an instance was requested as its first argument. > >>> The remaining arguments are those passed to the object constructor > >>> expression (the call to the class). The return value of __new__() > >>> should be the new object instance (usually an instance of cls).""" > >> > >> I was actually thinking about cdef classes, where __new__ is much more > >> subtle. I didn't realize it was a static method that takes the class > >> as a first argument rather than just a class method. > > > > It needs to be to support inheritance. You usually call the __new__ > method > > of the superclass to create the instance that you return. So you must be > > able to pass the required class through the hierarchy explicitly. > > Good point, I hadn't thought about that. > > - Robert > _______________________________________________ > Cython-dev mailing list > [email protected] > http://codespeak.net/mailman/listinfo/cython-dev > It could also work with a classmethod, because you'd be using super(cls, cls).__new__(), which also ensures that the subclass is passed as the first argument to __new__ in superclasses. Of course, type(TheClass).__call__ will pass the TheClass as the first argument, so if you make __new__ a classmethod it will need to take the class as two arguments.
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