PEP 318: Can't we all just get along?

[Michael J. Fromberger]

In article <mailman.1891.1092854353.5135.python-list at python.org>,
 Paul Morrow <pm_mon at yahoo.com> wrote:

> Michael J. Fromberger wrote:
> 
> > In article <mailman.1858.1092832530.5135.python-list at python.org>,
> >  Paul Morrow <pm_mon at yahoo.com> wrote:
> >>    class Foo:
> >>       def method1(self, a, b): pass       # clearly an instance method
> >>       def method2(cls, a, b): pass        # clearly a class method
> >>       def method3(a, b): pass             # clearly a static method
> > 
> > I think this is a terrible idea.  What you are proposing is essentially 
> > that Python should assign special meaning to the identifiers "self" and 
> > "cls" when they appear as the first variable in a method definition 
> > inside a class.  I am having a hard time thinking of anything LESS in 
> > the spirit of Python, short of writing in unstructured BASIC.
> 
> 'self' already has a special meaning to experienced Python developers, 
> by virtue of its role in the recommended coding practices.

That's true:  And note, that its special meaning is interpreted not by 
the Python translator, but by the Python programmer.  It is my feeling
that it should remain thus.

> And if you ask experienced Python developers who understand the 
> difference between class, static, and instance methods, to guess what 
> kind of method this is...
> 
>      def foo(cls, a, b): pass
> 
> ...I bet the majority would correctly guess "class".

Well, given just that definition, the guess would be incorrect.  The 
current release of Python would also require:

   def foo(cls, a, b): pass  # As defined above
   foo = classmethod(foo)

Otherwise, it would be an instance method, not a class method.  I hope 
this illustrates why visual conventions are not always as obvious as 
they seem, and should not be cast into the concrete of implementation.

> Right.  So a convention becomes a rule.  Sounds like a natural 
> evolution.

And just like in natural evoluation, not all mutations are desirable. ;)

> Declarations aren't needed when an obvious interpretation of the code 
> conveys the desired meaning.

What about when the obvious interpretation of the code does NOT convey 
the desired meaning?

-M

-- 
Michael J. Fromberger             | Lecturer, Dept. of Computer Science
http://www.dartmouth.edu/~sting/  | Dartmouth College, Hanover, NH, USA