[Python-Dev] LOAD_NAME & classes (original) (raw)

Guido van Rossum guido@python.org
Tue, 23 Apr 2002 12:02:28 -0400

> 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/)