- With
nums = [3, 1], which exception does while True: nums.pop() eventually raise? Answer: IndexError
while True never stops on its own. After both items are removed, pop() is called on an empty list and raises IndexError. StopIteration is wrong: while loops do not raise it. Only iterators do, inside for loops or next().
- Starting with
n = 1, which loop leaves n equal to 16? Answer: while n < 16: n *= 2
Doubling from 1 gives 2, 4, 8, 16. At 16 the test n < 16 is false, so n stays 16. With <=, 16 still passes the test, and n doubles once more to 32.
- After
n = 10 and c = 0, what is c after while n > 1: n //= 2; c += 1 runs? Answer: 3
Both statements after the colon are in the loop body. n goes 10 to 5 to 2 to 1, so c becomes 3. At n = 1 the test n > 1 fails. Getting 4 means looping while n > 0, which would add one more step from 1 to 0.
- With
i = 0, which loop prints 0, 1 and 2, each on its own line? Answer: while i < 3: print(i); i += 1
Printing before adding 1, while i < 3, prints 0, 1 and 2. Putting the increment first shifts the output to 1, 2, 3. Using <= 3 adds an extra pass that prints 3.
- In Python, when does the
else block attached to a while loop run? Answer: When the condition turns false without a break
A while loop's else runs when the loop ends because its condition became false. A break skips it. The block is not like finally, so leaving through break does not trigger it. It also runs whether the body executed zero times or many times.
