Hi, the behaviour I always observed when creating instances by calling the class A is that '__init__' is always only called when the object returned by A.__new__ is an instance of A. This can be observed by the following code:
class A(object):
def __new__(cls, *args, **kwds):
print "A.__new__", args, kwds
return object.__new__(B, *args, **kwds)
def __init__(cls, *args, **kwds):
print "A.__init__", args, kwds
class B(object):
def __new__(cls, *args, **kwds):
print "B.__new__", args, kwds
return object.__new__(cls, *args, **kwds)
def __init__(cls, *args, **kwds):
print "B.__init__", args, kwds
Interactively A() then gives:
>>> A()
A.__new__ () {}
<__main__.B object at 0xb7bed0ec>
Yet [1] says: "[...] some rules for __new__: [...] If you return an
object of a different class, its __init__ method will be called."
Am I missing something? Is this documented somewhere else? Also it
would be nice if someone could point me to the function that implements
this in C. I didn't find anything in object.c or typeobject.c.
Best regards
Frank Benkstein.
[1] http://www.python.org/download/releases/2.2/descrintro/#__new__
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