Home Original page

Guido's new method definition idea

Ben Kaplan bsk16 at case.edu
Mon Dec 8 12:21:08 EST 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.
More information about the Python-list mailing list