Raising errors — making your code fail loudly on purpose (step 6/9) · error handling

promptdojo_›phase 02 · real python›ch 09 · error handling

lesson 3 of 3 · raising errors — making your code fail loudly on purposestep 6 / 9

Claude shipped this and a teammate spent two days debugging a "missing data" bug. validate_order calls int(qty) which raises ValueError on bad input, the except: pass swallows it, and the function falls through to return None. The caller has no idea anything went wrong.

Replace the try/except block so bad input fails loudly with a raise ValueError("qty must be positive"). The call site already has the right try/except to print the message.

Expected output:

qty must be positive

The break is on lines 2, 3, 4, 5, 6, 7 — but read the whole snippet first.

⌘↵ runs the editor.read, then continue.

Replace the try/except block so bad input fails loudly with a raise ValueError("qty must be positive"). The call site already has the right try/except to print the message.

Expected output:

qty must be positive

The break is on lines 2, 3, 4, 5, 6, 7 — but read the whole snippet first.

this step needs the editor

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Raising errors — making your code fail loudly on purpose — step 6 of 9

this step needs the editor