CMU Unit 3 Practice Test

What is the centerY of c after we press the mouse once, according to the code below?

• 255

• 205

• 245

• 195

Answer explanation

The circle is created with a starting y-value of 250. After 1 click, the centerY of c is decreased by 5, leaving 245. The center Y of g is not relevant.

What is the centerY of c after we press the mouse once, according to the code below?

• 210

• 110

• 125

• 225

Answer explanation

On line 3, c is added to group g with the g.add(c) command.

On line 6, g.centerY affects c because c is now in the group. On line 7, c moves again, for a total of 25 pixels of increase between lines 6-7.

Since c has a starting y-value of 100, then it increases to 125.

Which shapes remains visible in the group after we press and release the mouse?

• r and s

• o and r

• o and s

• c and s

Answer explanation

On mouse press, s is removed from the group, however it is added back in the group on mouse released. So s is still visible after mouse press and release.

o is drawn and never made invisible or removed, so will still be visible.

c is invisible because of line 13, and r is invisible because of line 17.

What is the centerY of c after we run the code?

• 105

• 205

• 305

• 405

Answer explanation

c is created on line 2 and never added to the group. Then on line 4, a for loop runs the code 'c.centerY += 5' for each shape in g.children. Since g has only 1 shape, then 'c.centerY += 5' only runs once.

c has a starting y-value of 100, and since c.centerY += 5 only runs once, c's y-value ends at 105.

What is the centerY of c after we run the code?

• 100

• 105

• 300

• 305

Answer explanation

c is created with a y-value of 100. It is never added to the group. The code on lines 4-5 only affect the y-values of each shape in the group, so c remains unaffected. c's final yvalue is still 100.

Which of the following will not be printed?

• 0

• 1

• 2

• 3

Answer explanation

i will take on 3 values starting at 0: 0, 1, 2.

Another way to think about it is that i will go from 0 to 1 less than 3, so 0 to 2.

Which of the following will not be printed?

• 3

• 4

• 5

• 6

Answer explanation

i will take on the values within 3 and 1 less than 6.

So 3, 4, 5

What will count.value be after the program is run and the mouse is clicked once?

• 2

• 3

• 4

• 5

Answer explanation

Count is created on line 6 with a starting value of 0.

When the program is run, the for loop on lines 8-9 will increase count.value by 2 each time the for loop repeats. Since the for loop repeats 3 times (i = 0, 1, 2), count.value is now 6.

After the mouse is pressed, the for loop on lines 12-13 decreases count.value by 1 for each shape in the shapes group. Since there are 3 shapes in the group, count.value decreases by 1 three times. So now count.value is 3.

How many times will hello be printed?

• 2

• 3

• 6

• 5

Answer explanation

The for loop on line one repeats twice. The for loop on line 2 repeats 3 times, printig the word hello.

So for i = 0, the for loop on line 2 repeats three times, printing hello three times.

For i = 1, the for loop on line 2 repeats three times, printing hello three more times.

Total: 6

Which of the following is the correct syntax to create a list of nums 5, 6, 7, and 8?

• nums = [5, 6, 7, 8]

• nums = (5, 6, 7, 8)

• nums = [5 6 7 8]

• nums = "5, 6, 7, 8"

Answer explanation

The correct syntax to create a list is

<name of list> = [item 1, item 2, item 3, ...]