On 7/24/07, Sandra-24 <[EMAIL PROTECTED]> wrote: > On Jul 24, 5:20 am, Bruno Desthuilliers <bruno. > [EMAIL PROTECTED]> wrote: > > IIRC, __new__ is supposed to return the newly created object - which you > > are not doing here. > > > > class Bar(Foo): > > def __new__(cls, a, b, c, *args): > > print 'Bar.__new__', len(args) > > if not args: > > cls = Zoo > > obj = super(Bar, cls).__new__(cls, a, b, c, *args) > > if not args: > > obj.__init__(a, b, c, 7) > > return obj > > Thanks guys, but you are right Bruno, you have to return the newly > created object or you get: > > >>> b = Bar(1,2,3) > Bar.__new__ 0 > Foo.__new__ 3 > Zoo.__init__ 4 > Foo.__init__ 3 > >>> b is None > True > > However, if you return the object you get: > > >>> b = Bar(1, 2, 3) > Bar.__new__ 0 > Foo.__new__ 3 > Zoo.__init__ 4 > Foo.__init__ 3 > Traceback (most recent call last): > File "<input>", line 1, in <module> > TypeError: __init__() takes exactly 5 arguments (4 given) > > Which is the same blasted error, because it seems to want to call init > on the returned object and it's calling it with 4 args :( Is there any > way around that? >
__init__ is going to be called with the arguments passed to __new__ and there doesn't seem to be any way to affect that. Your only option to make it not happen is for Zoo not to be a subclass of Bar. Possible workarounds: Each subclass of Bar needs a corresponding __new__ Each subclass of Bar needs a cooperating __init__ that detects (via optional arguments) if it's being called by Bar.__new__ or directly and noops in the second case. -- http://mail.python.org/mailman/listinfo/python-list
