Validate Input Before Processing
Try it: Validate Input Before Processing
How a program reads untrusted text with input() and checks it in order (empty line, conversion with try / except, allowed range) before it computes anything, re-prompting after each rejected line. Switch a check off, or run the range check before converting, to see which bad input slips through or crashes the program.
How it works
- input() always returns a str, even when the user types digits.
- Check 1: an empty line (line.strip() == "") is rejected first; the loop prints a message and continue goes back to input().
- Check 2: float(line) / int(line) inside try; a non-numeric line raises ValueError and the except block recovers instead of crashing.
- Check 3: a converted number outside the allowed range is still invalid and is rejected (the range check must come after the conversion: comparing the str itself raises TypeError).
- The first line that passes every check breaks out of the loop and is processed: overtime pay (1.5x only for hours above 40), ordered grade bands, or a ticket total.
Default run (21 steps): The overtime pay program is ready. 4 input lines are queued for input(). … print shows Pay: 475.0.
Simplified: Three fixed programs (you change the input lines and switch the checks, never the code); the lab implements their Python semantics itself and nothing is executed as Python. Every combination was run in CPython 3.12 with the same inputs and the lab reproduces its output and error messages. input() returns the lines you type, one per call (the prompt is not printed), and raises EOFError when they run out. Input is printable ASCII only.
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