[Python-ideas] Implementing __dir__ (moving dir implementation to object.__dir__?)

[Michael Foord]

On 23 May 2011 19:16, Michael Foord <fuzzyman at gmail.com> wrote:

> Hello all,
>
> I'm looking at implementing __dir__ for a class (mock.Mock as it happens)
> to include some dynamically added attributes, the canonical use case
> according to the documentation:
>
>
> http://docs.python.org/dev/reference/datamodel.html?highlight=__dir__#object.__dir__
>
> What I would like to do is report all the "standard attributes", and then
> add any dynamically created attributes.
>
> So the question is, how do I obtain the "standard list" (the list that dir
> would normally report in the absence of a custom __dir__ implementation)?
>
> There is no object.__dir__ (despite the fact that this is how it is
> documented...) and obviously calling dir(self) within __dir__ is doomed to
> failure.
>
> The best I have come up with is:
>
> def __dir__(self):
>     return dir(type(self)) + list(self.__dict__) +
> self._get_dynamic_attributes()
>


Better version which orders and removes duplicates:

        return sorted(set((dir(type(self)) + list(self.__dict__) +
self._get_dynamic_attributes()))


>
> This works (absent multiple inheritance), but it would be nice to just be
> able to do:
>
> def __dir__(self):
>     standard = super().__dir__()
>     return standard + self._get_dynamic_attributes()
>
> Moving the relevant parts of the implementation of dir into object.__dir__
> would be one way to solve that.
>
> All the best,
>
> Michael Foord
>
> --
>
> http://www.voidspace.org.uk/
>
> May you do good and not evil
> May you find forgiveness for yourself and forgive others
> May you share freely, never taking more than you give.
> -- the sqlite blessing http://www.sqlite.org/different.html
>
>
>


-- 

http://www.voidspace.org.uk/

May you do good and not evil
May you find forgiveness for yourself and forgive others
May you share freely, never taking more than you give.
-- the sqlite blessing http://www.sqlite.org/different.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20110523/b3880066/attachment.html>