Guido's new method definition idea

Ben Kaplan bsk16 at case.edu
Mon Dec 8 18:21:08 CET 2008



On Dec 8, 2008, at 11:59 AM, anthony.tolle at gmail.com wrote:

> On Dec 6, 4:15 pm, Carl Banks <pavlovevide... at gmail.com> wrote:
>> On Dec 6, 12:47 am, "Patrick Mullen" <saluk64... at gmail.com> wrote:
>>
>>> Could I do something like this:
>>
>>> def a.add(b): return a+b
>>
>>> Outside of a class?  Of course then that makes you think you could  
>>> do
>>> 5.add(6) or something craaaazy like that.  (I mean, you can do
>>> (5).__add__(6) but that's something else entirely)
>>
>> I'd be inclined to think that this defines an instancemethod on an
>> existing object a.  In other word, I'd read the following two lines  
>> as
>> more or less equivalent.
>>
>> def a.add(b): return a+b
>>
>> a.add = lambda b: a+b
>>
>> Just as the following are equivalent:
>>
>> def foo(): return bar
>>
>> foo = lambda: bar
>>
>> I had been -0 on this, but now I think I'm -1.
>
> This brings up another question, what would one use when referencing
> method names inside the class definition?:
>
> class C:
>    def self.method(arg):
>        self.value = arg
>    def self.othermethod(arg):
>        self.value = arg
>    # do this?
>    funcs = (self.method, self.othermethod)
>    # or this?
>    funcs = (method, othermethod)
>
> On another related note, I would be interested in seeing this syntax
> adopted for a different purpose...
>
> Normally, if I'm defining a nested function that needs to be stored as
> an object attribute, I have to use a dummy name, like the following:
>
> class C:
>    def createfunc(self, arg):
>        def _dummy(arg):
>             return arg + 1
>        self.func = _dummy
>
> It would be nice to be able to do the following instead:
>
> class C:
>    def createfunc(self):
>        def self.func(arg):
>            return arg + 1
>
> Or, after the class definition is done, to extend it dynamically:
>
> def C.method(self, arg):
>    self.value = arg
>
> ...which would be the equivalent of the following:
>
> def method(self, arg):
>    self.value = arg
> C.method = method
>
> Since functions are first-class objects, it seems perfectly reasonable
> to me.
> --
> http://mail.python.org/mailman/listinfo/python-list

I agree, this would be much nicer and would not require any special  
cases. I'm not convinced that this is needed, but at least this won't  
confuse newbies as much.



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