[Python-Dev] "groupby" iterator

[Guido van Rossum]

> How about:
> 
> extract(attr='grade')
> extract(item=2)
> extract(method='foo')   # returns the result of calling 'ob.foo()'
> 
> And following the pattern of Zope's old "query" package:
> 
> extract(extract(attr='foo'), attr='bar')   # extracts ob.foo.bar
> extract(extract(item=10), method='spam')   # extracts ob[10].spam()
> 
> i.e., the first (optional) positional argument to extract is a function 
> that's called on the outer extract's argument, and the return value is then 
> used to perform the main extract operation on.

I'm not sure what the advantage of this is.  It seems more typing,
more explanation, probably more code to implement (to check for
contradicting keyword args).

> IIRC, the Zope query package used __getitem__ instead of __call__ on its 
> instances as a speed hack, but I don't think we should follow that example.  :)

Right. :)

--Guido van Rossum (home page: http://www.python.org/~guido/)