Aaaargh! "global name 'eggz' is not defined"

[kj]

How can one check that a Python script is lexically correct?

As my Python apps grow in complexity and execution, I'm finding it
more often the situation in which a program dies after a lengthy
(i.e. expensive) run because the execution reaches, say, a typo.
Of course, this typo needs to be fixed, but I'd like to find out
about it before I waste hours on a run that is bound to fail.  Is
there any way to do this?  I imagine the answer is no, because
given Python's scoping rules, the interpreter can't know about
these things at compile time, but I thought I'd ask.

TIA!

kynn