Chapter 4

Checkpoints

What is a loop iteration?

An execution of the statements in the body of the loop.

Does the while loop test its condition before or after it performs an interation?

Before

How many times will ‘Hello World’ be printed in the following program?

count = 10

while count < 1:

• print (‘Hello World’)

None. The condition count < 0 will be false to begin with.

What is an infinite loop?

A loop that has no way of stopping and repeats until the program is interrupted.

Rewrite the following code so it calls the range function instead of using the list

[0, 1, 2, 3, 4, 5]:

for x in [0, 1, 2, 3, 4, 5]:

• print (‘ love to program!’)

for x in range (6):

• print(‘I love to program!’)

What will the following code display?

for number in range (6):

• print (number)

0

1

2

3

4

5

What will the following code display?

For number in range (2, 6):

• print (number)

2

3

4

5

What will the following code display?

for number in range (10, 5, -1)

• print (number)

10

9

8

7

6

What is an accumulator?

A variable that is used to accumulate the total of a series of numbers.

What will the following code display?

total = 0

for count in range (1, 6):

• total = total + count

print (total)

15

What will the following code display?

number 1 = 10

number 2 = 5

number 1 = number 1 + number 2

print (number1)

print (number2)

15

5

Rewrite the following statements using augmented assignment operators:

• quantity = quantity + 1

• days_left = days_left - 5

• price = price * 10

• price = price / 2

quantity += 1

days_left -= 5

price *= 10

price /=2

What is a sentinel?

A sentinel is a special value that marks the end of a list of items.

Why should you take care to choose a distinctive value as a sentinel?

A sentinel value must be unique enough that it will not be mistaken as a regular value in the list.

What does the phrase “garbage in, garbage out” mean?

It means that bad data (grabage) is provided as input to a program, the program will produce bad data (garbage) as output.

What is a priming read? What is its purpose?

It is the input operation that takes place just before an input validation loop. The purpose of the priming read is to get the first input value.

If the input that is read by the priming read is valid, how many times will the input validation loop iterate?

None