On 2007-10-29, Steven Bethard <[EMAIL PROTECTED]> wrote:
> Hrvoje Niksic wrote:
>> Tommy Nordgren <[EMAIL PROTECTED]> writes:
>>
>>> Given the following:
>>> def outer(arg)
>>> avar = ''
>>> def inner1(arg2)
>>> # How can I set 'avar' here ?
>>
>> I don't think you can, until Python 3:
>> http://www.python.org/dev/peps/pep-3104/
>
> But it definitely does work in Python 3 if you use 'nonlocal'::
>
> Python 3.0a1+ (py3k:58681, Oct 26 2007, 19:44:30) [MSC v.1310 32 bit
> (Intel)] on win32
> Type "help", "copyright", "credits" or "license" for more
> information.
> >>> def f():
> ... x = 1
> ... def g():
> ... nonlocal x
> ... x = 2
> ... print(x)
> ... g()
> ... print(x)
> ...
> >>> f()
> 1
> 2
>
> That said, I'd like to see the reason you think you want to do
> this.
It's allows a standard programming idiom which provides a
primitive form of object oriented programming using closures to
represent state.
def account(opening_balance):
balance = opening_balance
def get_balance():
nonlocal balance
return balance
def post_transaction(x):
nonlocal balance
balance += x
return balance, post_transaction
fred_balance, fred_post = account(1500)
joe_balance, joe_post = account(12)
fred_post(20)
joe_post(-10)
fred_balance()
1520
joe_balance()
2
Python classes will of course nearly always win, though the idiom
looks like it might be faster (I don't have Python 3000 to try it
out).
--
Neil Cerutti
It isn't pollution that is hurting the environment; it's the impurities in our
air and water that are doing it. --Dan Quayle
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