[Python-3000] Generic function PEP won't make it in time

[Emin.shopper Martinian.shopper]

On 4/25/07, Josiah Carlson <jcarlson at uci.edu> wrote:
>
>
> If your unit tests take hours to run, then you aren't going to get
> anything useful from the ABC requirements for hours either (unless you
> are pre-instantiating everything you are going to use during program
> execution, in which case this could become your unittest).


No, the ABC requirements are checked as soon as a module is imported (i.e.,
classes are checked at definition time not when an instance is created). I
have been using my own ABC implementation for quite a while and it has
repeatedly proven it's value when I create a new derived class and forget to
implement a necessary method.

Please remember that this isn't about Java style type checking and
> verification during compilation.  This is, strictly speaking, ABC
> checking on object instantiation, method invocation, and possibly even
> argument verification.  This isn't the magic bullet you are looking for
> (you'll have to go to one of those static typed languages for that).


Again, I disagree. With metaclasses it is easy and useful to have checking
at class definition (see
http://web.mit.edu/~emin/www/source_code/py_abc/abc.py for an example of
what I mean). Generally I don't want static checking, but occasionally it is
nice to have something like that and ABCs provide a good way to do that.

I'm not claiming that is the only benefit of ABCs. I'm just pointing out
what I find to be a very useful feature of ABCs that I hope makes into
python.
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