Macros in Python?

[Jp Calderone]

On Wed, Apr 09, 2003 at 08:58:04PM +0200, Dominic wrote:
> 
> 
> (defmacro with-root-privs (() &body body)
>   (let ((oldidsym (gensym)))
>     `(let ((,oldidsym (geteuid)))
>        (seteuid 0)
>        (unwind-protect
> 	   (progn , at body)
> 	 (seteuid ,oldidsym)))))
> 
> Is there an easy way to produce similar code
> in Python which gurantees that certain things
> happen around some code? (Maybe by using
> generators?)

  Yay metaclasses yay!

    class WrapperMetaclass:
        def __init__(self, prefix, wrapper):
            self.prefix = prefix
            self.wrapper = wrapper
        def __call__(self, name, bases, attrs):
            for k in attrs:
                if k.startswith(self.prefix):
                    attrs[k] = self.wrapper(attrs[k])
            return type(name, bases, attrs)

> [snip]
> 
> Is something like this feasible?
> 
> def server(a,b):
>   if cond:
>       ...
>   else:
>     With_Root_Privs:
>        if x in user:
>           active.append(x)
>          (...)
> 

    def acquireRoot():
        # Whatever
    def releaseRoot():
        # Whatever
    def superuserWrapper(f):
        def function(*args, **kw):
            acquireRoot()
            try:
                f(*args, **kw)
            finally:
                releaseRoot()
        return function

  class Server(object):
      __metaclass__ = WrapperMetaclass('asroot_', superuserWrapper)

      def asroot_addUser(self, x):
          active.append(x)

      def checkCondition(self, a, b):
          if cond:
              ....
          else:
              self.asroot_addUser(x)

  Jp

> -- 
> http://mail.python.org/mailman/listinfo/python-list

-- 
Lowery's Law:
        If it jams -- force it.  If it breaks, it needed replacing anyway.
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