Home Original page

Storing objects required by functions.

Christos TZOTZIOY Georgiou tzot at sil-tec.gr
Tue Dec 30 21:04:47 EST 2003 
On 31 Dec 2003 00:08:47 GMT, rumours say that bokr at oz.net (Bengt
Richter) might have written:

>The other way is to take advantage of functions' roles as decriptors and the mechanism that
>makes bound methods with a self as the first arg, but the rest apparently normal. I.e,
>we can put the r parameter in the place of self (not specifically tested)
>
>    def uses_self(r, x):
>        pass
>    uses_self = uses_self.__get__(re.compile("..."))

It's much more general to use new.instancemethod.  See:

def voodoo(function, *its_arguments):
    from new import instancemethod
    def child(function, first_argument, *rest_of_arguments):
        if rest_of_arguments:
            return child(
                instancemethod(function, first_argument, object),
                *rest_of_arguments
            )
        else:
            return instancemethod(function, first_argument, object)
    return child(function, *its_arguments)

The import statement is in the voodoo just for completeness including it
here.
The function above recurses in order to allow stuff like:

getter = voodoo(getattr, my_object, "its_attribute")

or the more modern

getter = voodoo(operator.itemgetter("its_attribute"), my_object)

and similarly

setter = voodoo(operator, my_object, "its_attribute")

allowing

setter(value)

at good speeds.


I have a module predicates.py defining All and Any classes for
iterables, and the trick above plus itertools allows *some* operations
to run faster than correspondent python code...
-- 
TZOTZIOY, I speak England very best,
Ils sont fous ces Redmontains! --Harddix
More information about the Python-list mailing list