Pre-defining an action to take when an expected error occurs

[Tempo]

John Machin  thanks for all of your help, and I take responsibility for
the way I worded my sentences in my last reply to this topic. So in an
effort to say sorry, I want to make it clear to everybody that it seems
as though errors in my code and use of external programs (Excel in
particular) are making "range(sh.nrows)" have faulty results. I am
trying to pinpoint the spot in my code or use of Excel, before
"range(sh.nrows) is executed, that is bugged. John Machin, I am
thrilled that the package xlrd exists at all because it simplifies a
daunting task for a beginner programer--me. Its uses are not bound to
beginners either. So thanks for the package and your help to this point.