No swap function in Python?

[Bjorn Pettersen]

> From: Ben Wolfson [mailto:wolfson at uchicago.edu]
> In article <slrn9hd2cs.iiu.scarblac at pino.selwerd.nl>, "Remco Gerlich"
> <scarblac at pino.selwerd.nl> wrote:
> >
> > A swap function is impossible in Python. A function cannot 
> rebind names
> > in the caller's namespace. This is why del is a statement and not a
> > function, for instance.
> 
> >>> a = 10
> >>> b = 5
> >>> def swap(**d):
>         assert len(d) == 2, 'Only swaps two variables!'
>         import sys
>         loc = sys._getframe(1).f_locals
>         k1, k2 = d.keys()
>         loc[k1] = d[k2]
>         loc[k2] = d[k1]
> 
> >>> swap(a=a, b=b)
> >>> print a, b
> 5 10
> >>>

But...

def foo():
   a = 10
   b = 5
   swap(a=a, b=b)
   print a,b
	
foo()

still prints 10 5...

real-locals-aren't-writable'ly y'rs
-- bjorn