[Python-ideas] For-loop variable scope: simultaneous possession and ingestion of cake

[George Sakkis]

On Mon, Oct 13, 2008 at 8:09 AM, Arnaud Delobelle <arnodel at googlemail.com>wrote:

> Since this idea didn't get much steam, a more modest proposal would be to
> > relax the restriction on cells: allow the creation of new cells and the
> > rebinding of func_closure in pure Python. Then one could explicitly
> create a
> > new scope without any other change in the language through a 'localize'
> > decorator that would create a new cell for every free variable (i.e.
> global
> > or value from an enclosing scope) of the function:
> >
> > lst = []
> > for i in range(10):
> >    @localize
> >    def f(): print i
> >    lst.append(f)
> >    lst.append(localize(lambda: i**2))
> >
> > I'd love to be proven wrong but I don't think localize() can be
> implemented
> > in current Python.
>
> I think you probably can in CPython, but that would involve bytecode
> introspection and using ctypes.pythonapi.PyCell_New, and it would be
> terribly inefficient.  I wrote a similar decorator that takes a
> function and bind some of its variables to some values. e.g
>
> @bind(x=40, y=2)
> def foo(): return x+y
>
> >>> foo()
> 42
>
> It's useless of course.


Can you expand a bit on that ? Why would it be terribly inefficient and why
is it useless ?

George
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20081013/eafd5718/attachment.html>