staticmethod vs metaclass

[Robin Becker]

A colleague wanted to initialize his class __new__ and tried code resembling this

############### ########1
class Metaclass (type):
def __init__(cls, name, bases, *args, **kwargs):
super(Metaclass , cls).__init__(c ls, name, bases, *args, **kwargs)
print 'cls=',cls, cls.__new
cls.__new__ = staticmethod(cl s.__new)

def __new(self,cls, *args):
print 'new(',self,cls ,args,')'
return object.__new__( cls,*args)

class A:
__metaclass__ = Metaclass
def __init__(cls,*a rgs):
print '__init__(',cls ,args,')'
A(3,4,5)
############### ########
cls= <class '__main__.A'> <bound method Metaclass.__new of <class '__main__.A'>>
new( <class '__main__.A'> <class '__main__.A'> (3, 4, 5) )
__init__( <__main__.A object at 0x008D0AB0> (3, 4, 5) )
############### ########

We wanted to eliminate the extra self argument in the constructed class __new__
so tried
############### ########2
class Metaclass (type):
def __init__(cls, name, bases, *args, **kwargs):
super(Metaclass , cls).__init__(c ls, name, bases, *args, **kwargs)
print 'cls=',cls, cls.__new
cls.__new__ = staticmethod(st aticmethod(cls. __new))

def __new(cls,*args ):
print 'new(',cls,args ,')'
return object.__new__( cls,*args)

class A:
__metaclass__ = Metaclass
def __init__(cls,*a rgs):
print '__init__(',cls ,args,')'
A(3,4,5)
############### ########
cls= <class '__main__.A'> <bound method Metaclass.__new of <class '__main__.A'>>
Traceback (most recent call last):
File "mmm.py", line 15, in ?
A(3,4,5)
TypeError: 'staticmethod' object is not callable
############### ########

A bit puzzling, but after thought we found both the following do what we want
with the __new__ argument signature.
############### ########3
class Metaclass (type):
def __init__(cls, name, bases, *args, **kwargs):
super(Metaclass , cls).__init__(c ls, name, bases, *args, **kwargs)
print 'cls=',cls, cls.__new
cls.__new__ = staticmethod(cl s.__new)

def __new(cls,*args ):
print 'new(',cls,args ,')'
return object.__new__( cls,*args)
__new = staticmethod(__ new)

class A:
__metaclass__ = Metaclass
def __init__(cls,*a rgs):
print '__init__(',cls ,args,')'
A(3,4,5)
############### ########
cls= <class '__main__.A'> <function __new at 0x008D60F0>
new( <class '__main__.A'> (3, 4, 5) )
__init__( <__main__.A object at 0x008D0C10> (3, 4, 5) )
############### ########

############### ########4
class Metaclass (type):
def __init__(cls, name, bases, *args, **kwargs):
super(Metaclass , cls).__init__(c ls, name, bases, *args, **kwargs)
print 'cls=',cls, cls.__new
cls.__new__ = cls.__new

def __new(cls,*args ):
print 'new(',cls,args ,')'
return object.__new__( cls,*args)
__new = staticmethod(st aticmethod(__ne w))

class A:
__metaclass__ = Metaclass
def __init__(cls,*a rgs):
print '__init__(',cls ,args,')'

A(3,4,5)
############### ########
cls= <class '__main__.A'> <staticmethod object at 0x008D0B90>
new( <class '__main__.A'> (3, 4, 5) )
__init__( <__main__.A object at 0x008D0D90> (3, 4, 5) )
############### ########

This does what we want in terms of the signature, but we aren't calling the
correct super __new__, any ideas how we can do that?
--
Robin Becker