At 07:32 AM 5/1/2006 -0700, Guido van Rossum wrote:
>On 4/30/06, Ben Wing <[EMAIL PROTECTED]> wrote:
> > [1] ideally, change this behavior, either for 2.6 or 3.0. maybe have a
> > `local' keyword if you really want a new scope.
> > [2] until this change, python should always print a warning in this
> > situation.
> > [3] the current 'UnboundLocal' exception should probably be more
> > helpful, e.g. suggesting that you might need to use a `global foo'
> > declaration.
>
>You're joking right?
While I agree that item #1 is a non-starter, it seems to me that in the
case where the compiler statically knows a name is being bound in the
module's globals, and there is a *non-argument* local variable being bound
in a function body, the odds are quite high that the programmer forgot to
use "global". I could almost see issuing a warning, or having a way to
enable such a warning.
And for the case where the compiler can tell the variable is accessed
before it's defined, there's definitely something wrong. This code, for
example, is definitely missing a "global" and the compiler could in
principle tell:
foo = 1
def bar():
foo+=1
So I see no problem (in principle, as opposed to implementation) with
issuing a warning or even a compilation error for that code. (And it's
wrong even if the snippet I showed is in a nested function definition,
although the error would be different.)
If I recall correctly, the new compiler uses a control-flow graph that
could possibly be used to determine whether there is a path on which a
local could be read before it's stored.
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