[Python-3000] Draft PEP for outer scopes

[Michael Urman]

>    def weird(local=True):
>        if local:
>            n = 1
>        else:
>            global n   # [ or nonlocal n, in Nick's ]
>            n += 1
>        return n

I'm not sure what you're both trying to explain here. First off, the
above code yields a SyntaxWarning. Secondly all its accesses to n are
global accesses. The global keyword is currently a modifier for the
whole function. Thus the local parameter is misleading; it should be
called reset.

<stdin>:1: SyntaxWarning: name 'n' is assigned to before global declaration
>>> dis.dis(weird)
  2           0 LOAD_FAST                0 (local)
              3 JUMP_IF_FALSE           10 (to 16)
              6 POP_TOP

  3           7 LOAD_CONST               1 (1)
             10 STORE_GLOBAL             1 (n)
             13 JUMP_FORWARD            11 (to 27)
        >>   16 POP_TOP

  6          17 LOAD_GLOBAL              1 (n)
             20 LOAD_CONST               1 (1)
             23 INPLACE_ADD
             24 STORE_GLOBAL             1 (n)

  7     >>   27 LOAD_GLOBAL              1 (n)
             30 RETURN_VALUE

Would you expect the overloaded global keyword to apply differently,
or just have slightly different scoping semantics? Would a nonlocal
keyword apply differently? Would we allow multiple function-global
parameter modifiers?

I personally expect that while there is a theoretical clash between
variable names in nested scopes, that's already a poor coding
decision. The module level globals should not unintentionally collide
with function-local non-local access. Thus reusing the global keyword
is not a practical limitation.
-- 
Michael Urman  http://www.tortall.net/mu/blog