Odd behaviour of dir(object) with metaclasses.
dirk at gerrits.homeip.net
Thu Apr 10 08:18:32 CEST 2003
Tim Peters wrote:
> [Dirk Gerrits]
>>I am a bit puzzled by the behaviour of the dir builtin.
>>Why is there an unnatural (IMHO) distinction between type/class objects
>>and other non-module objects? I assume that a class's class is not
>>considered become dir comes from the pre-metaclass era?
> No, dir() was rewritten from scratch for 2.2. The comments in the C code
> /* Elif some form of type or class, grab its dict and its bases.
> We deliberately don't suck up its __class__, as methods belonging
> to the metaclass would probably be more confusing than helpful. */
> That's what Guido believed at the time, and I agreed at the time, so that's
> what the code does. Across at least seven pre-releases of 2.2, nobody
> disagreed <wink>.
Well I think its understandable, but in my mind, what dir does to
classes should be called something like instancedir. Anyway, I guess you
have a point. People who don't use metaclasses won't care anyway. And
those who do might not care either. ;)
>>Shouldn't the docs really read
> No, becuase the suggested rewording doesn't describe the actual behavior --
> as you noted above, the current wording does.
Yeah I meant to say 'Shouldn't the docs really read ... with the
behaviour changed accordingly?'. But I assume you'll say no to that as
>>I hope you'll be able to clarify these things for me a bit.
> dir() was meant to be a convenience in interactive mode, and that's all.
> Because of that, no two people will agree on what it "should do" in all
> respects in all cases. Changing it always makes people scream too, so I
> doubt it will be changed again. If you don't like what it does, write a dir
> that does what you like -- doing so in Python is easy enough.
Yes, one of Python's many great strengths. :)
Thanks for clearing this one up.
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