On 2010-09-22, at 5:50 PM, Steven D'Aprano wrote:
> On Thu, 23 Sep 2010 06:07:21 am Pete wrote:
>> For a plugin mechanism, I'm populating a dict with calls to the
>> implemented plugins.
> [...]
>> Now I get that I need to instantiate foo and bar first before I can
>> refer to them in the dict.
>>
>> so something like
>>
>> foo_instance = foo()
>> bar_instance = bar()
>>
>> list = { 'foo': foo_instance.do(), 'bar': bar_instance.do() }
>>
>> would probably work. But is that the best/pythonic way to do it?
>
> (1) It's generally a bad idea to "shadow" the name of a built-in
> function like list. Particularly since your variable list isn't
> actually a list, but a mapping of name:function. Find a better
> name :)
That was just for the example, of course, but point taken :)
> (2) You end up calling the do() methods inside the dict. You probably
> mean to save the method itself as a callback function.
I did.
> (3) There's no need to keep the instances floating around as
> independent names, unless you need direct access to them.
>
> Putting these together, we get:
>
> dispatch_table = { 'foo': foo().do, 'bar': bar().do }
>
> Which you then later call using:
>
> dispatch_table[name](args)
>
> where name is "foo" or "bar", and args is anything you need to pass to
> the do() method.
I see. And are those methods then unbound? (Because when instantiating the
object it needs to do some initialization of instance variables,
and I think those were not available when calling an unbound method. (My
understanding of the bound/unbound method distinction is rather vague at this
point,
I apologise)
> Oh, and (4)... in Python circles, it's traditional but not compulsory
> to use metasyntactic variables named after Monty Python sketches
> rather than foo and bar. So spam, ham, eggs, parrot (dead or
> otherwise), names of cheeses, aardvark..., although there is no
> standard order.
>
> Indeed, when I design my killer language, the identifiers "foo" and
> "bar" will be reserved words, never used, and not even mentioned in
> the reference manual. Any program using one will simply dump core
> without comment. Multitudes will rejoice. -- Tim Peters, 29 Apr 1998
THANK YOU!
It's this kind of knowledge that I crave, sir.
:)
- Pete
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