Syntactically, while loops look just like for loops. They both have a keyword, a colon, and a list to iterate over.

Select one answer, then check.

• True
  Not quite. A while loop has no list to iterate over: after the keyword while comes a condition, as in an if statement.
• False
  Correct. Both start with a keyword and end their first line with a colon, but a while loop has a condition where a for loop has a list.

A While loop will always execute at least once.

Select one answer, then check.

• True
  Not quite. The condition is checked before the body runs the first time; if it is false then, the program skips the body entirely.
• False
  Correct. If the condition is false the first time it is checked, the body never runs.

The program below will NOT loop forever.

count = 10
while count >= 0:
    count = count - 1
print(count)

Select one answer, then check.

• True
  Correct. count goes down by one on every pass, so it reaches -1 and the condition count >= 0 becomes false.
• False
  Not quite. count goes down by one on every pass, so once it reaches -1 the condition count >= 0 is false and the loop ends.

The program below will NOT loop forever.

count = 0
while count > 0:
    count = count + 1
print(count)

Select one answer, then check.

• True
  Correct. count starts at 0, so count > 0 is false the first time it is checked: the body never runs, and the program prints 0.
• False
  Not quite. The body would increase count forever, but it never runs: count > 0 is already false when count is 0.

The program below will NOT loop forever.

alpha = 'dog'
while alpha == 'dog':
    alpha = 'cat'
    print(alpha)
    alpha = 'dog'
print(alpha)

Select one answer, then check.

• True
  Not quite. alpha is 'cat' only in the middle of the body; by the end of every pass it is 'dog' again, so the condition is true every time it is checked.
• False
  Correct. The condition is only checked at the start of each pass, and by then alpha is always back to 'dog', so the loop never ends.

The program below will NOT loop forever.

while True:
    print("Loop again")

Select one answer, then check.

• True
  Not quite. The condition is the value True, which never becomes false, and nothing in the body stops the loop.
• False
  Correct. The condition is the value True, which never changes, so the loop prints Loop again forever.

while loops are more common in Python than for loops because they are safer.

Select one answer, then check.

• True
  Not quite. for loops are the most common form of iteration in Python, and they are the safer one: they end when the list runs out, while a while loop can easily loop forever by accident.
• False
  Correct. It is the other way around: for loops are more common, and safer, because they end when the list runs out.

A while loop will execute once for each expression in the conditional.

Select one answer, then check.

• True
  Not quite. The number of passes has nothing to do with the expressions in the condition: the body repeats for as long as the condition is true.
• False
  Correct. A while loop repeats its body for as long as the condition is true, however many expressions the condition has.

Which of the following have a body?

Select every answer that applies, then check.

• while loop
  Correct. The indented statements under the while line are its body.
• for loop
  Correct. The indented statements under the for line are its body, which runs once for each element.
• Function definition
  Correct. The indented statements under the def line are the body of the function.
• Function call
  No body. A call runs the body of a function that was defined elsewhere; the call itself has no indented block.
• if statement.
  Correct. The indented statements under the if line are its body.
• Dictionary access
  No body. Looking up a value is an expression, not a block of indented statements.