object references

[bruno at modulix]

Steven D'Aprano wrote:
> On Sat, 25 Mar 2006 21:33:24 -0800, DrConti wrote:
> 
> 
>>Dear Python developer community,
>>I'm quite new to Python, so perhaps my question is well known and the
>>answer too.
>>
>>I need a variable alias ( what in other languages you would call  "a
>>pointer" (c) or "a reference" (perl))
> 
> 
> Others have given you reasons why you can't do this, or shouldn't do this.
> In general, I agree with them -- change your algorithm so you don't
> need indirect references. 
> 
> But if you can't get away from it, here is another work-around that might
> help:

(snip)

And another one, that mess less with attributes (but more with lookup
rules - use it at your own risks !-):

class CompoundAttribute(object):
  def __init__(self, *names):
    self._names = names
  def __get__(self, obj, objtype):
    if obj is None:
       return self
    return [getattr(obj, name) for name in self._names]
  def __set__(self, obj, value):
    raise TypeError, "object '%s' does not support assignement" % self

import types


class ObjectClass(object):
  def __getattribute__(self, name):
    v = object.__getattribute__(self, name)
    if not isinstance(v, types.FunctionType) \
       and hasattr(v, '__get__'):
      return v.__get__(self, self.__class__)
    return v


> instance = ObjectClass()
  instance.attribute = 'First PK Elem'
  instance.another_attribute = 'Second PK Elem'
  instance.identifier = CompoundAttribute('attribute', 'another_attribute')

NB : Sorry, not tested.


-- 
bruno desthuilliers
python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in 'onurb at xiludom.gro'.split('@')])"