[PyQt] support for __slots__ / no-__dict__ instances in SIP/PyQt?

Phil Thompson phil at riverbankcomputing.com
Thu Nov 4 11:07:10 GMT 2010

On Wed, 3 Nov 2010 15:36:32 +0100, Hans Meine
<meine at informatik.uni-hamburg.de> wrote:
> Hi Phil,
> I have the personal habit of using __slots__ to explicitly list all
> "member 
> variables", i.e. instance attributs my classes have.  IIRC, the original

> intention behind this was to allow for efficient classes, i.e. ones that
> do 
> not have one __dict__ per instance.  But as a side effect, this leads to

> exceptions being thrown when one tries to add attributes that were not 
> specified, and I am using this as a desired constraint, i.e. I want to
> force 
> myself to specify the attributes I use in the class, as a sort of
> developer 
> documentation.
> However, this fails as soon as one of the base classes has a __dict__,
> guess what?  QObject and friends have.
> Is there a good reason why this must be the case, or would it be a
> desirable 
> feature of SIP to suppress the __dict__s?  (BTW: boost::python does so 
> unconditionally.)

The good reason is that it is a useful feature and removing it would break
many applications.

> I can imagine that people are used to "attaching" data members to
> but 
> I would happily ditch this and instead get notified about incomplete 
> __slots__.

While SIP could be enhanced to have that as an option, PyQt would never
use it.


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