[Python-ideas] Keyword only argument on function call

Chris Barker chris.barker at noaa.gov
Tue Sep 11 04:12:56 EDT 2018

On Mon, Sep 10, 2018 at 11:00 PM, Ethan Furman <ethan at stoneleaf.us> wrote:

> In my day job I spend a lot of time writing/customizing modules for a
> framework called OpenERP (now Odoo*).  Those modules are all subclasses,
> and most work will require updating at least a couple parent methods -- so
> most calls look something like:
>   def a_method(self, cr, uid, ids, values, context=None):
>     ...
>     super(self, parent).a_method(cr, uid, ids, values, context=context)

hmm -- this is a trick -- in those cases, I find myself using *args,
**kwargs when overloading methods. But that does hide the method signature,
which is really unfortunate. IT works pretty well for things like GUI
toolkits, where you might be subclassing a wx.Window, and the docs for
wx.Window are pretty easy to find, but for you own custom classes with
nested subclassing, it does get tricky.

For this case, I kinda like Steve Barnes idea (I think it is his) to have a
"magic object of some type, so you can have BOTH specified parameters, and
easy access to the *args, **kwargs objects. Though I'm also wary of the

Perhaps there's some way to make it explicit, like "self":

def fun(a, b, c, d=something, e=something, &args, &&kwargs):

(I'm not sure I like the &, so think of it as a placeholder)

In this case, then &args would be the *args tuple, and &&kwargs would be
the **kwargs dict (as passed in) -- completely redundant with the position
and keyword parameters. So the above could be:

def a_method(self, cr, uid, ids, values, context=None, &args, &&kwargs):
    super(self, parent).a_method(*args, **kwargs)
    do_things_with(cr, uid, ...)

So you now have a clear function signature, access to the parameters, and
also a clear an easy way to pass the whole batch on to the superclass'

I just came up with this off teh top of my head, so Im sure there are big
issues, but maybe it can steer us in a useful direction.



Christopher Barker, Ph.D.

Emergency Response Division
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Chris.Barker at noaa.gov
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