Hi.
[Mark Hammond]
> The point isn't about my suffering as such. The point is more that
> python-dev owns a tiny amount of the code out there, and I don't believe we
> should put Python's users through this.
>
> Sure - I would be happy to "upgrade" all the win32all code, no problem. I
> am also happy to live in the bleeding edge and take some pain that will
> cause.
>
> The issue is simply the user base, and giving Python a reputation of not
> being able to painlessly upgrade even dot revisions.
I agree with all this.
[As I imagined explicit syntax did not catch up and would require
lot of discussions.]
[GvR]
> > Another way is to use special rules
> > (similar to those for class defs), e.g. having
> >
> > <frag>
> > y=3
> > def f():
> > exec "y=2"
> > def g():
> > return y
> > return g()
> >
> > print f()
> > </frag>
> >
> > # print 3.
> >
> > Is that confusing for users? maybe they will more naturally expect 2
> > as outcome (given nested scopes).
>
> This seems the best compromise to me. It will lead to the least
> broken code, because this is the behavior that we had before nested
> scopes! It is also quite easy to implement given the current
> implementation, I believe.
>
> Maybe we could introduce a warning rather than an error for this
> situation though, because even if this behavior is clearly documented,
> it will still be confusing to some, so it is better if we outlaw it in
> some future version.
>
Yes this can be easy to implement but more confusing situations can arise:
<frag>
y=3
def f():
y=9
exec "y=2"
def g():
return y
return y,g()
print f()
</frag>
What should this print? the situation leads not to a canonical solution
as class def scopes.
or
<frag>
def f():
from foo import *
def g():
return y
return g()
print f()
</frag>
[Mark Hammond]
> > This probably won't be a very popular suggestion, but how about pulling
> > nested scopes (I assume they are at the root of the problem)
> > until this can be solved cleanly?
>
> Agreed. While I think nested scopes are kinda cool, I have lived without
> them, and really without missing them, for years. At the moment the cure
> appears worse then the symptoms in at least a few cases. If nothing else,
> it compromises the elegant simplicity of Python that drew me here in the
> first place!
>
> Assuming that people really _do_ want this feature, IMO the bar should be
> raised so there are _zero_ backward compatibility issues.
I don't say anything about pulling nested scopes (I don't think my opinion
can change things in this respect)
but I should insist that without explicit syntax IMO raising the bar
has a too high impl cost (both performance and complexity) or creates
confusion.
[Andrew Kuchling]
> >Assuming that people really _do_ want this feature, IMO the bar should be
> >raised so there are _zero_ backward compatibility issues.
>
> Even at the cost of additional implementation complexity? At the cost
> of having to learn "scopes are nested, unless you do these two things
> in which case they're not"?
>
> Let's not waffle. If nested scopes are worth doing, they're worth
> breaking code. Either leave exec and from..import illegal, or back
> out nested scopes, or think of some better solution, but let's not
> introduce complicated backward compatibility hacks.
IMO breaking code would be ok if we issue warnings today and implement
nested scopes issuing errors tomorrow. But this is simply a statement
about principles and raised impression.
IMO import * in an inner scope should end up being an error,
not sure about 'exec's.
We will need a final BDFL statement.
regards, Samuele Pedroni.
