Control Flow and Looping Flashcards

What is the output of: ```python result = [i for i in range(10) if i % 3 == 0] print(result) ```

Answer: [0, 3, 6, 9]

range(10) produces 0-9; filtering by i%3==0 keeps 0, 3, 6, 9.

What is the output of: ```python i = 0 while i < 3: i += 1 print(i) ```

Answer: 3

The loop runs while i < 3, incrementing i each time; after the loop i equals 3.

Which of the following correctly uses `all()` to check that every number in a list is positive?

Answer: all(x > 0 for x in nums)

all() with a generator expression returns True only if every element satisfies the condition.

What is the output of: ```python for char in 'abc': if char == 'b': continue print(char) ```

Answer: a c

continue skips 'b', so only 'a' and 'c' are printed.

What does this code print? ```python found = False for n in [4, 8, 15, 16]: if n > 10: found = True break print(found, n) ```

Answer: True 15

The first n > 10 is 15, which sets found=True and breaks, leaving n as 15.

What is the Pythonic way to loop a fixed number of times without needing the loop variable?

Answer: for _ in range(n): ...

Using _ as the loop variable signals that the variable is intentionally unused, which is the Python convention.

What is the output of: ```python for i in range(1, 4): print(i * '*') ```

Answer: * ** ***

i * '*' repeats the star i times: '*', '**', '***' for i=1,2,3.