is it a bug in exec?

[long]

Of cause your code runs well. But if you remove the "global foo" in
main(), it will fail. And it will succeed again if you call exec(t1)
directly. I think this behavior is strange. Even I pass a shadow copy
of globals and locals to exec, it still fails. So perhaps there is a
basic difference between exec(t1,dg,dl) and
exec(t1,globals(),locals()). What do you think about it? Thanks.


On Jan 21, 2:14 am, Steven D'Aprano <steve
+comp.lang.pyt... at pearwood.info> wrote:
> On Thu, 20 Jan 2011 20:52:15 -0800, longqian9... at gmail.com wrote:
> > In pyhton 3.1, I found the following code will succeed with argument 1
> > to 4 and fail with argument 5 to 9. It is really strange to me. I
> > suspect it may be a buy in exec() function. Does anyone have some idea
> > about it? Thanks.
>
> What makes you think it's a bug? Is there anything in the documentation
> of exec that suggests to you that some other behaviour should occur? What
> version of Python are you using?
>
> Without knowing what behaviour you expect and what behaviour you see, how
> are we supposed to know if you've found a bug or not?
>
> I suggest you fire up the interactive interpreter and try this:
>
> t1 = """
> class foo:
>     def fun():
>         print('foo')
>
> def main():
>     global foo
>     foo.fun()
>
> main()
> """
>
> dg = {}
> dl = {}
>
> exec(t1, dg, dl)
>
> then inspect the values of dg and dl and see if it helps. If not, write
> back with what you expect to happen, and what you see instead.
>
> --
> Steven