Python exceptions: practice questions with answers.

What this topic tests

• Catch the specific exception you expect, not every error.
• Trace try, except, else, and finally in order.
• Raise a clear exception instead of returning a misleading value.

Common mistakes

• Using a bare except and swallowing programming mistakes.
• Putting too much code inside the try block, including code that cannot fail in the expected way.
• Assuming finally runs only when an exception occurs.

Ten representative questions from the full bank. Try each one before opening the answer.

1. Multiple choiceq0972

   1. Ming must close the shop whether or not the milk tea succeeds. When does finally run in try-except-finally?

   1. only on an exception
   2. only when there is no exception
   3. always, whether or not there is an exception
   4. never
   Show answer

   Answer

   C. always, whether or not there is an exception

   Why: The finally block runs on every exit path: normal completion, a caught exception, an uncaught one, and even a return inside try. That is why cleanup belongs there.

2. Multiple choiceq0980

   2. Ming writes `except Exception` before `except ValueError`. What happens to the ValueError branch?

   1. it never runs
   2. it still runs first
   3. it raises SyntaxError
   4. it runs twice
   Show answer

   Answer

   A. it never runs

   Why: Handlers are tested top to bottom and the first match wins. Exception covers every ordinary error, including ValueError, so the later specific branch is dead code.

3. Multiple choiceq0985

   3. 🧋 What happens with a bare raise that has no exception type?

   1. it re-raises the current exception
   2. it raises RuntimeError
   3. it does nothing
   4. it is an error
   Show answer

   Answer

   A. it re-raises the current exception

   Why: A bare raise inside except re-raises the exception being handled and keeps its original traceback. It is the idiom for logging and then letting the caller decide.

4. Multiple choiceq1000

   4. Converting the user input 'abc' to an integer fails. Which exception is usually raised?

   1. FileNotFoundError
   2. ValueError
   3. KeyError
   4. TypeError
   Show answer

   Answer

   B. ValueError

   Why: int('abc') fails on content, not on type, so ValueError. TypeError would mean you passed something like None or a list. The message names the actual string.

5. Fill in the blankq0974

   5. Ming wants the file closed even if writing fails. Which keyword opens it safely?

   ____ open('orders.txt', 'w') as f:
       f.write('latte')

   Show answer

   Answer

   with

   Why: The with statement uses the file's context manager, which closes it on normal exit and on exception, replacing a try/finally. The as f part binds the open file.

6. Fill in the blankq0993

   6. Which keyword catches an exception in a try statement?

   Show answer

   Answer

   except

   Why: except names the exception type to handle and introduces the handler block. try only marks the code being watched. finally is for cleanup, not catching.

7. Fill in the blankq0998

   7. Raise an exception deliberately. Which keyword goes in the blank?

   if price < 0:
       ____ ValueError('price cannot be negative')

   Show answer

   Answer

   raise

   Why: raise ValueError(...) rejects the bad price with a message the caller can show. The condition guards it, so valid prices pass through.

8. Output predictionq0973

   8. After an exception is caught, does finally still run? What is printed?

   try:
       print(1 / 0)
   except ZeroDivisionError:
       print("boom")
   finally:
       print("end")

   Show answer

   Answer

   boom
   end

   Why: 1/0 raises ZeroDivisionError, so except prints boom; finally then runs and prints end. The traceback is suppressed because the exception was handled.

9. Output predictionq0987

   9. A calculator catches a division by zero. What is printed?

   try:
       print(10 / 0)
   except ZeroDivisionError:
       print("safe")

   Show answer

   Answer

   safe

   Why: 10 / 0 raises before print runs, so try produces no output; the handler then prints safe. The failed print never printed anything.

10. Output predictionq1004

    10. Use a default when conversion fails. What is printed?

    text = 'abc'
    try:
        qty = int(text)
    except ValueError:
        qty = 0
    print(qty)

    Show answer

    Answer

    0

    Why: int('abc') raises ValueError, the handler assigns qty = 0, and print shows 0. qty is defined because the except branch always runs on failure.

Common questions