static variables?

[Gerhard Häring]

In article <3DDA583F.3070206 at Linux.ie>, Padraig Brady wrote:
> Josh wrote:
>> Hi guys,
>> 
>> I am a python newbie, and I am sure there is an easy answer but, Is there
>> any equivalent to C's static variables in Python? If not, how can you have
>> variables inside a function, that 'remember' their values between function
>> calls?
>> 
>> Josh
> 
> For functions you could set attributes of the function
> as static variables? like:
> 
> def func():
>      func.name="value"
> 
> Then the attribute will be stored with the function
> and so is as long lived as the function

Yes, *but* func.name="value" will be executed on every function call. In
realistic examples, you'll want to change the value of the 'static' variable,
so you'll end up with code like:

    def foo():
        print foo.counter
        foo.counter += 1
    foo.counter = 0

or, even uglier:

    def foo():
        if not hasattr(foo, 'counter'):
            foo.counter = 0
        print foo.counter
        foo.counter += 1

I dare to say that if you really need to keep state, then going the
object-oriented way and using a class is the natural solution.

Alternatively, you can create your own callables, which is a lot more flexible
than faking 'static functions', anyway:

    class Foo:
        def __init__(self, startval):
            self.counter = startval

        def __call__(self):
            print self.counter
            self.counter += 1

    foo = Foo(5) # start counting at 5

    foo()
    foo()

HTH,
-- 
Gerhard Häring
OPUS GmbH München
Tel.: +49 89 - 889 49 7 - 32
http://www.opus-gmbh.net/