Chapter 7

Question 1

Graphics

Answer 1

Discipline that underlies the representation and display of geometric
shapes in two‐ and three‐dimensional space

Question 2

Turtle Graphics

Answer 2

Toolkit provides a simple and enjoyable way to draw pictures
in a window
- turtle is a non-standard, open-source Python module

Question 3

How did turtle graphics originally develop?

Answer 3

I was part of the children’s programming language Logo
- Created by Seymour Papert and his colleagues at MIT in the late 1960s
- Analogy: Turtle crawling on a piece of paper, with a pen tied to its tail
* Sheet of paper is a window on a display screen
* Position specified with (x, y) coordinates- Cartesian coordinate system, with origin (0, 0) at the center of a window

Question 4

Heading

Answer 4

Specified in degrees, the heading or direction increases in value as
the turtle turns to the left, or counterclockwise. Conversely, a
negative quantity of degrees indicates a right, or clockwise, turn. the
turtle is initially facing east, or 0 degrees. North is 90 degree.

Question 5

color

Answer 5

Initially black, the color can be changed to any of more than 16
million other colors.

Question 6

Width

Answer 6

This is the width of the line drawn when the turtle moves. The initial
width is 1 pixel.

Question 7

Down

Answer 7

This attribute, which can be either true or false, controls whether the
turtle’s pen is up or down. When true (that is, when the pen is down),
the turtle draws a line when it moves. When false (that is, when the
pen is up), the turtle can move without drawing a line.

Question 8

Interface

Answer 8

set of methods of a given class
- Used to interact with an object
- Use docstring mechanism to view an interface
help(<class>)
help(<class>.<method>)</method></class></class>

Question 9

Turtle graphics configuration file (turtle.cfg) contains initial settings of several attributes which are?

Answer 9

Turtle, Screen, and Canvas objects
- Python creates default settings for these attributes
- to open a file with these settings: Open a text editor, enter the settings, and save the file as turtle.cfg

Question 10

What must you do before applying methods to an object?

Answer 10

create the object (i.e., an instance)

Question 11

instantiation

Answer 11

process of creating an object

Question 12

Use a ____ to instantiate an object

Answer 12

• constructor
  syntax:

<variable> = <class>(<any>)
for Turtle class:
t = Turtle()
</any></class></variable>

Question 13

To close a turtle’s window, click its ___ box

Answer 13

close
- attempting to manipulate a turtle whose window has been closed raises an
error

Question 14

Vector graphics

Answer 14

Drawing of 2 dimensional shapes, such as rectangles, triangles, and circles

Question 15

Mutator methods

Answer 15

methods that change the internal state of a Turtle object

Question 16

Accessor methods

Answer 16

methods that return the values of a Turtle object’s
attributes without altering its state

Question 17

Manipulating a Turtle’s screen

Answer 17

• Access a turtle’s Screen object using the notation t.screen
• Then call a Screen method with this object
• Methods window_width() and window_height() can be used to locate the
  boundaries of a turtle’s window

Question 18

Pixels

Answer 18

The colored dots called picture elements that make up the display area on a computer screen
- ach pixel represents a color – the default is black - Change the color by running the pencolor method

Question 19

RGB

Answer 19

common system for representing colors
- stands for red, green and blue
- Each color component can range from 0 – 255
* 255 - max saturation of a color component
* 0 - total absence of that color component
- a true color system
- Each color component requires 8 bits; total number of bits needed to represent
a color value is 24

Question 20

What is the total number of RGB colors?

Answer 20

2^24 (16,177,216)

Question 21

The Turtle class includes a ___ method for changing the turtle’s drawing color

Answer 21

• pencolor
• expects integers for the three RGB components