[Python-Dev] reducing self.x=x; self.y=y; self.z=z boilerplate code (original) (raw)

Phillip J. Eby pje at telecommunity.com
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 "adoptinitargs" workaround: http://phenix-online.org/cctbxsources/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().

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