What are python closures realy like?

[Fredrik Lundh]

"Paddy" wrote:

> I played around a bit. The following is a 'borg'  version in that there
> is only one counter shared between all calls of the outer function:
>
>>>> def fun_borg_var(initial_val=0):
> ...    def borg_var_inc(x=1):
> ...        fun_borg_var._n += x

a drawback with the function attribute approach compared to a real closure
is that the function is no longer a self-contained callable:

def fun_borg_var(initial_val=0):
    def borg_var_inc(x=1):
        fun_borg_var._n += x
        return fun_borg_var._n
    def borg_var_dec(x=1):
        fun_borg_var._n -= x
        return fun_borg_var._n
    try:
        fun_borg_var._n = fun_borg_var._n
    except:
        fun_borg_var._n = initial_val
    return (borg_var_inc, borg_var_dec)

up1, dn1 = fun_borg_var()

del fun_borg_var # won't need this any more

print up1() # oops!

so you might as well use a good old global variable, and initialize it as
usual.

</F>