a = b = 1 just syntactic sugar?

Terry Reedy tjreedy at udel.edu
Sun Jun 8 02:51:26 CEST 2003


"Ed Avis" <ed at membled.com> wrote in message
news:l1wufxh9g8.fsf at budvar.future-i.net...
> Steven Taschuk <staschuk at telusplanet.net> writes:
>
> >We already have closures, don't we?
> >
> >    >>> def f(x):
> >    ...     def g(y):
> >    ...         return x + y
> >    ...     return g
> >    ...
> >    >>> q = f(3)
> >    >>> q(4)
> >    7
>
> Which Python version does this require?

2.1 with future statement, 2.2 without

>  (The machine to hand has only 1.5.2, although normally I use 2.2 or
so.)

Upgrade if you can.

> I mean things like
>
>   def make_adder():
>     x = 0
>     def incr():
>       x += 1
>       return x
>     return incr
>
>   f = make_adder()
>   g = make_adder()
>   print f(), f(), g(), g() # 1 2 1 2

You can read but not rebind variable in outer scope.  But this works:

def make_counter():
  counter = [0]
  def incr():
    counter[0] += 1
    return counter[0]
  return incr
>>> c1=make_counter()
>>> c2=make_counter()
>>> print c1(), c1(), c2(), c2()
1 2 1 2

Terry J. Reedy








More information about the Python-list mailing list