Another Language Change for Debate

Sun Jan 13 02:43:39 EST 2002

On Fri, 11 Jan 2002 21:10:21 -0600, Gareth McCaughan wrote:

> I much prefer a different approach.
> 
>     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>)
> which would make it possible, e.g., to define
> a function called "memo" which memoizes its argument
> and say (typical useless example follows):
>     def memo fib(n):
>         if n<2: return n
>         return fib(n-2)+fib(n-1)
> and get only O(n) calls to "fib" on doing fib(n).

You can achieve something similar with a metaclass:

class funcmodifier(type):
    def __init__(cls, name, bases, dict):
        super(funcmodifier, cls).__init__(name, bases, dict)
        replace = {}
        for name,value in dict.iteritems():
            if callable(value) and cls._isvalidname(name):
                modname, funcname = name.split('_',1)
                try:
                    f = sys._getframe(1) #caller's frame
                    mod = eval(modname, f.f_globals, f.f_locals)
                except NameError:     continue
                if not callable(mod): continue
                func = mod(value)
                replace[name] = (funcname, func)
        for name, (newname, func) in replace.iteritems():
            delattr(cls, name)
            setattr(cls, newname, func)
    def _isvalidname(name):
        if name.startswith('_'): return 0
        has_uscore = name.count('_')
        if has_uscore == 1 and name.endswith('_'): return 0
        return has_uscore
    _isvalidname = staticmethod(_isvalidname)

>>> class Hungarian:
	__metaclass__ = funcmodifier
	def classmethod_hovercraft(*a): print a
	def staticmethod_eels(*a): print a

>>> h = Hungarian()
>>> h.hovercraft('blah')
(<class '__main__.Hungarian'>, 'blah')
>>> h.eels('la','dee','da')
('la', 'dee', 'da')
>>> 

-- 
BTR    
BEN WOLFSON HAS RUINED ROCK MUSIC FOR A GENERATION
 -- Crgre Jvyyneq