On 5 Oct 2005 09:27:04 GMT, Duncan Booth <[EMAIL PROTECTED]> wrote: >Antoon Pardon wrote: > >> It also is one possibility to implement writable closures. >> >> One could for instace have a 'declare' have the effect that >> if on a more inner scope such a declared variable is (re)bound it >> will rebind the declared variable instead of binding a local name. > >That is one possibility, but I think that it would be better to use a >keyword at the point of the assigment to indicate assignment to an outer >scope. This fits with the way 'global' works: you declare at (or near) the >assignment that it is going to a global variable, not in some far away part >of the code, so the global nature of the assignment is clearly visible. The >'global' keyword itself would be much improved if it appeared on the same >line as the assignment rather than as a separate declaration. > >e.g. something like: > >var1 = 0 > >def f(): > var2 = 0 > > def g(): > outer var2 = 1 # Assign to outer variable > global var1 = 1 # Assign to global
IMO you don't really need all that cruft most of the time. E.g., what if ':=' meant 'assign to variable wherever it is (and it must exist), searching according to normal variable resolution order (fresh coinage, vro for short ;-), starting with local, then lexically enclosing and so forth out to module global (but not to builtins).' If you wanted to assign/rebind past a local var shadowing an enclosing variable var, you'd have to use e.g. vro(1).var = expr instead of var := expr. Sort of analogous to type(self).mro()[1].method(self, ...) Hm, vro(1).__dict__['var'] = expr could conceivably force binding at the vro(1) scope specifically, and not search outwards. But for that there would be optimization issues I think, since allowing an arbitrary binding would force a real dict creation on the fly to hold the the new name slot. BTW, if/when we can push a new namespace on top of the vro stack with a 'with namespace: ...' or such, vro(0) would still be at the top, and vro(1) will be the local before the with, and := can still be sugar for find-and-rebind. Using := and not finding something to rebind would be a NameError. Ditto for vro(n).nonexistent_name_at_level_n_or_outwards. vro(-1) could refer global module scope and vro(-2) go inwards towards local scope at vro(0). So vro(-1).gvar=expr would give you the effect of globals()['gvar']=expr with a pre-existence check. The pre-existence requirement would effectively be a kind of declaration requirement for the var := expr usage, and an initialization to a particular type could enhance inference. Especially if you could have a decorator for statements in general, not just def's, and you could then have a sticky-types decoration that would say certain bindings may be inferred to stick to their initial binding's object's type. Rambling uncontrollably ;-) My .02USD ;-) Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
