Carrying variables over from function to function

[Peter Otten]

Bruno Desthuilliers wrote:

> 2/ functional solution:
> -----------------------
> def make_funcs():
>     x = 0
>     def _abc():
>         x = 1
>         return x + 1
>     def _abcd():
>         return x + 1
>     return _abc, _abcd
> 
> abc, abcd = make_funcs()
> print abc()
> print abcd()

The x in function _abc() is not the same as that in make_funcs() and _abcd()
as you can easily verify by modifying _abc() to

    def _abc():
        x # raises UnboundLocalError
        x = 1
        return x + 1

Once a variable is assigned a value the compiler treats it as local to that
function. Closed-over variables are therefore always read-only, much to the
chagrin of Lisp-lovers.

Peter