DictProxy? What is this?

[digitalorganics@gmail.com]

When I tried to update a class's __dict__, I got an error saying that
there is no 'update' attribute for dictproxy object. What is a
dictproxy object? I thought that __dict__ is always suppose to be a, no
kidding, dictionary? Hence there should indeed be an update method.
What's this proxy business?

Thanks all.

[Fredrik Lundh]

Re: DictProxy? What is this?

digitalorganics @gmail.com wrote:
[color=blue]
> When I tried to update a class's __dict__, I got an error saying that
> there is no 'update' attribute for dictproxy object. What is a
> dictproxy object?[/color]

a CPython implementation detail, used to protect an internal data structure used
by new-style objects from unexpected modifications.

</F>

[digitalorganics@gmail.com]

Re: DictProxy? What is this?


Fredrik Lundh wrote:[color=blue]
> digitalorganics @gmail.com wrote:
>[color=green]
> > When I tried to update a class's __dict__, I got an error saying that
> > there is no 'update' attribute for dictproxy object. What is a
> > dictproxy object?[/color]
>
> a CPython implementation detail, used to protect an internal data structure used
> by new-style objects from unexpected modifications.
>
> </F>[/color]

Ah, so I'm not suppose to be able to change a class's __dict__? Thanks
Fredrik.

[Maric Michaud]

Re: DictProxy? What is this?

Le lundi 26 juin 2006 16:06, digitalorganics @gmail.com a écrit :[color=blue]
> Fredrik Lundh wrote:[color=green]
> > digitalorganics @gmail.com wrote:[color=darkred]
> > > When I tried to update a class's __dict__, I got an error saying that
> > > there is no 'update' attribute for dictproxy object. What is a
> > > dictproxy object?[/color]
> >
> > a CPython implementation detail, used to protect an internal data
> > structure used by new-style objects from unexpected modifications.
> >
> > </F>[/color]
>
> Ah, so I'm not suppose to be able to change a class's __dict__? Thanks
> Fredrik.[/color]

Of course, yes :

In [1]: class a(object) : pass
...:

In [2]: a.__dict__
Out[2]: <dictproxy object at 0xa7e01d34>

In [3]: a.__dict__.item s()
Out[3]:
[('__dict__', <attribute '__dict__' of 'a' objects>),
('__module__', '__main__'),
('__weakref__', <attribute '__weakref__' of 'a' objects>),
('__doc__', None)]

In [4]: a.__dict__['foo'] = lambda s : True
---------------------------------------------------------------------------
exceptions.Type Error...

TypeError: object does not support item assignment

hmmm, not this way, but :

In [5]: a.foo = lambda s : True

In [6]: a.__dict__.item s()
Out[6]:
[('__dict__', <attribute '__dict__' of 'a' objects>),
('__module__', '__main__'),
('foo', <function <lambda> at 0xa79528ec>),
('__weakref__', <attribute '__weakref__' of 'a' objects>),
('__doc__', None)]

In [7]: a().foo()
Out[7]: True

or :

In [9]: setattr(a, 'bar', lambda s : False)

In [10]: a().bar()
Out[10]: False


--
_____________

Maric Michaud
_____________

Aristote - www.aristote.info
3 place des tapis
69004 Lyon
Tel: +33 426 880 097

[digitalorganics@gmail.com]

Re: DictProxy? What is this?

All right. Thanks for explaining that Maric.

Maric Michaud wrote:[color=blue]
> Le lundi 26 juin 2006 16:06, digitalorganics @gmail.com a écrit :[color=green]
> > Fredrik Lundh wrote:[color=darkred]
> > > digitalorganics @gmail.com wrote:
> > > > When I tried to update a class's __dict__, I got an error saying that
> > > > there is no 'update' attribute for dictproxy object. What is a
> > > > dictproxy object?
> > >
> > > a CPython implementation detail, used to protect an internal data
> > > structure used by new-style objects from unexpected modifications.
> > >
> > > </F>[/color]
> >
> > Ah, so I'm not suppose to be able to change a class's __dict__? Thanks
> > Fredrik.[/color]
>
> Of course, yes :
>
> In [1]: class a(object) : pass
> ...:
>
> In [2]: a.__dict__
> Out[2]: <dictproxy object at 0xa7e01d34>
>
> In [3]: a.__dict__.item s()
> Out[3]:
> [('__dict__', <attribute '__dict__' of 'a' objects>),
> ('__module__', '__main__'),
> ('__weakref__', <attribute '__weakref__' of 'a' objects>),
> ('__doc__', None)]
>
> In [4]: a.__dict__['foo'] = lambda s : True
> ---------------------------------------------------------------------------
> exceptions.Type Error...
>
> TypeError: object does not support item assignment
>
> hmmm, not this way, but :
>
> In [5]: a.foo = lambda s : True
>
> In [6]: a.__dict__.item s()
> Out[6]:
> [('__dict__', <attribute '__dict__' of 'a' objects>),
> ('__module__', '__main__'),
> ('foo', <function <lambda> at 0xa79528ec>),
> ('__weakref__', <attribute '__weakref__' of 'a' objects>),
> ('__doc__', None)]
>
> In [7]: a().foo()
> Out[7]: True
>
> or :
>
> In [9]: setattr(a, 'bar', lambda s : False)
>
> In [10]: a().bar()
> Out[10]: False
>
>
> --
> _____________
>
> Maric Michaud
> _____________
>
> Aristote - www.aristote.info
> 3 place des tapis
> 69004 Lyon
> Tel: +33 426 880 097[/color]