Another Language Change for Debate

Sat Jan 12 10:06:48 EST 2002

Tim Peters wrote:

[I suggested the following:]
> >
> >     class MyClass:
> >         def staticmethod bar(y):
> >             blah()
> >             stuff += stuff
> >         def classmethod baz(z):
> >             return 1
> >
> > This generalizes in an obvious way:
> >     def <name1> <name2>(<formals>): <body>
> > turns into
> >     def <name2>(<formals>): <body>
> >     <name2> = <name1>(<name2>)
[etc]
> 
> It's more that a gazillion "toy parser" tools out there (from Emacs
> python-mode to Python's own pyclbr.py) would have to be changed too, lest
> they all end up thinking you have an unbounded number of methods named
> "staticmethod" (etc).  You won't take this seriously until a dozen legacy
> tools you don't even remember you're using break <wink>.

Ah yes. That would be a shame. So here's a variant.

    class MyClass:
        def bar(y) [staticmethod]:
            do_some_stuff()
            return 123

By the way, if you define generator(x) to be the same
as iter(x) then that lets you say

    def f(x) [generator]:
        while 1:
            yield x
            x=x+1

after which f *is* a generator, not a function that returns
a generator. I don't think this is worth doing :-).

The manic generalizer in me wants to add that if you have
several modifiers you want to apply to a function or method,
you can say

    def f(x) [memoized,classmethod,ignoring_errors]:
        <stuff>

but I'm not sure whether that's elegant or gratuitous
just yet. By the way, for anyone who's curious, here are
rough approximations to the first and last of those
modifiers:

    def memoized(f):
        d = {}
        def _(*args):
            try: return d[args]
            except KeyError:
                result = f(*args)
                d[args] = result
                return result
        return _

    def ignoring_errors(f):
        def _(*args):
            try: return f(*args)
            except: return None
        return _

Note that "ignoring_errors" may be a misleading name,
since an error will still terminate execution of the
underlying function.

-- 
Gareth McCaughan  Gareth.McCaughan at pobox.com
.sig under construc