[Python-Dev] LOAD_NAME & classes

[Guido van Rossum]

> > Might it make more sense to issue a warning at compile time to the effect
> > that a variable is being used before it's assigned? How completely are
> 
> Hard to make sure, so, it would always be "MIGHT be used before
> assignment".  E.g.,
> 
> def f():
>     for i in range(6):
>         if i>0: print x,
>         x = str(i)
> 
> this is OK... no UnboundNameError.  Now, change the if's guard to
>         if SolveTuringHaltingProblem(i): print x,
> to see why it's hard to make sure about this at compile time.
> 
> A warning might still be OK of course, even though it may need to
> be worded in wishy-washy "might" terms -- this IS peculiar usage.

GCC warns about this stuff as soon as there's a path through the code
that could leave a variable unassigned, even if the path may not be
reachable depending on what other functions do, and while it
occasionally caused my to insert a useless initialization, I've
usually found that it was hard enough to prove to myself that the
initialization was unneeded to make me happy to insert it.

--Guido van Rossum (home page: http://www.python.org/~guido/)