On 29/05/13 07:27, PJ Eby wrote:
On Tue, May 28, 2013 at 3:41 PM, Russell E. Owen <ro...@uw.edu> wrote:
Is it true that this cannot be used for instance and class methods? It
dispatches based on the first argument, which is "self" for instance
methods, whereas the second argument would almost certainly be the
argument one would want to use for conditional dispatch.
You can use a staticmethod and then delegate to it, of course. But it
probably wouldn't be too difficult to allow specifying which argument
to dispatch on, e.g.:
@singledispatch.on('someArg')
def my_method(self, someArg, ...):
...
[...]
So, it's just a few lines added, but of course additional doc, tests,
etc. would have to be added as well. (It also might be a good idea
for there to be some error checking in wrapper() to raise an
approriate TypeError if len(args)<=arg.)
I feel that specifying the dispatch argument in full generality is overkill,
and that supporting two use-cases should be sufficient:
- dispatch on the first argument of functions;
- dispatch on the second argument of methods, skipping self/cls.
After all, is this not supposed to be *simple* generics? :-)
I'm vaguely leaning towards @singledispatch and @singledispatch.method for the
colour of this bike shed.
--
Steven
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