Guido's new method definition idea

[Chris Rebert]

On Sat, Dec 6, 2008 at 1:33 PM, Carl Banks <pavlovevidence at gmail.com> wrote:
> On Dec 5, 8:21 pm, "Daniel Fetchinson" <fetchin... at googlemail.com>
> wrote:
>> Hi folks,
>>
>> The story of the explicit self in method definitions has been
>> discussed to death and we all know it will stay. However, Guido
>> himself acknowledged that an alternative syntax makes perfect sense
>> and having both (old and new) in a future version of python is a
>> possibility since it maintains backward compatibility. The alternative
>> syntax will be syntactic sugar for the old one. This blog post of his
>> is what I'm talking about:
>>
>> http://neopythonic.blogspot.com/2008/10/why-explicit-self-has-to-stay...
>>
>> The proposal is to allow this:
>>
>> class C:
>>     def self.method( arg ):
>>         self.value = arg
>>         return self.value
>>
>> instead of this:
>>
>> class C:
>>     def method( self, arg ):
>>         self.value = arg
>>         return self.value
>
>
>
> -1
>
> I explained why deep in the thread but I'll elaborate more here.  When
> I see a def statement, I mentally equate that to an assigment to the
> thing being def'ed.  So for instance, when I see this:
>
>  def <something>():
>
> I think of it like this:
>
>  <somthing> = <the defined function>
>
>
> Thus, if I were to see a function definition like this
>
>  def foo.bar(): return 1
>
> I would think you were defining a function and assigning it to
> foo.bar.  IOW, it would be mostly equivalent to this:
>
>  foo.bar = lambda: 1
>
>
> (Analogously, I would expect a definition like this:
>
>  def baz[10](): return 1
>
> to be equivalent to this:
>
>  baz[10] = lambda: 1  )
>
>
> So, if, inside a class definition, I were to see this:
>
>  def self.method(): return 1
>
> Well, I'd understand that is was a method assigment, of course, but it
> would conflict with what I would expect the natural meaning of
> something like def a.b() would be.  The above statement is not
> equivalent to:
>
>  self.method = lambda: 1
>
> but I think that's what it ought to be, in general.

Similarly, to those coming from Ruby or those operating under the
frequent misunderstanding that the `def`s are happening in the context
of a class object (which in reality has yet to be created), `self` in
this context might be misconstrued as the class object and thus `def
self.foo` might be misunderstood (through the intuitive equivalence
you mention) as a defining a classmethod rather than an instance
method.

I also strongly echo the TOOWTDI arguments against adding this
duplicative syntax. It's a minor gain but costs much more than it's
worth for violating The Zen.

Cheers,
Chris

-- 
Follow the path of the Iguana...
http://rebertia.com

>
>
>
> Carl Banks
>
>
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