[Python-Dev] reducing self.x=x; self.y=y; self.z=z boilerplate code

Sat Jul 2 01:22:20 CEST 2005

At 03:59 PM 7/1/2005 -0700, Ralf W. Grosse-Kunstleve wrote:
>Hi,
>>I often find myself writing:
>> class grouping:
>> def __init__(self, x, y, z):
> self.x = x
> self.y = y
> self.z = z
>>I hate it, and every time I show this to a Python newcomer I get that
>skeptic look. How about this for a change?
>> class grouping:
>> def __init__(self, .x, .y, .z):
> pass

This extends to any number of arguments:
 class grouping:
 def __init__(self, x, y, z):
 self.__dict__.update(locals())
 del self.self
Or if you prefer a more generic approach:
 def initialize(ob, args):
 if 'self' in args:
 del args['self']
 for k, v in args.items():
 setattr(ob,k,v)
 class grouping:
 def __init__(self, x, y, z):
 initialize(self, locals())
There's really no need for special syntax here, if your goal is simply to 
reduce boilerplate.
>I'll write a PEP if I hear a few voices of support.

-1; there are lots of good solutions for this. For me, I usually have a 
base class with something like this:
 def __init__(self, **kw):
 for k, v in kw.items():
 if not hasattr(self.__class__, k):
 raise TypeError("%s has no %r attribute" % (self.__class__,k))
 else:
 setattr(self,k,v)
And then subclasses define their attributes and defaults using class 
attributes, properties, or other descriptors.
>(Otherwise I'll stick to my "adopt_init_args" workaround:
>http://phenix-online.org/cctbx_sources/libtbx/libtbx/introspection.py
>which does a similar job but doesn't look as elegant and is also
>quite inefficient).

There are more efficient solutions, especially __dict__.update().