Ch 4 Turtle Graphics

Question 1

attribute

Answer 1

Some state or value that belongs to a particular object. For example, tess (the turtle) has a color

Question 2

canvas

Answer 2

A surface within a window where drawing takes place. Where turtles can roam free.

Question 3

control flow

Answer 3

Loops, branches, and function calls. Loops = for and while loops. Branches = if, elif, else. Functions = ahem… functions

Question 4

for loop

Answer 4

A statement in Python for convenient repetition of statements in the body of the loop

Question 5

invoke

Answer 5

An object has methods. We use the verb invoke to mean activate the method. invoking a method is done by putting parentheses after the method name, with some possible arguments. So wn.exitonclick() is an invocation of the exitonclick method.

Question 6

instance

Answer 6

An object that belongs to a class. tess and alex (the Turtles) are different instances of the class Turtle.

Question 7

iteration

Answer 7

A basic building block for algorithms (programs). It allows steps to be repeated. Sometimes called looping.

Question 8

loop body

Answer 8

Any number of statements nested inside a loop. The nesting is indicated by the fact that the statements are indented under the for loop statement.

Question 9

loop variable

Answer 9

A variable used as part of a for loop. It is assigned a different value on each iteration of the loop, and is used as part of the terminating condition of the loop, when it can no longer get a further value.

Question 10

method

Answer 10

A function that is attached to an object. Invoking or activating the method causes the object to respond in some way, e.g. “forward” is the method when we say “tess.forward(100)”

Question 11

object

Answer 11

A “thing” to which a variable can refer. This could be a screen window, or one of the turtles you have created.

Question 12

range

Answer 12

A built-in function in Python for generating sequences of integers. It is especially useful when we need to write a for loop that executes a fixed number of times.

Question 13

sequential

Answer 13

The default behavior of a program. Step by step processing of an algorithm.

Question 14

terminating condition

Answer 14

A condition that occurs which causes a loop to stop repeating its body. break, continue, else, pass

Question 15

turtle

Answer 15

A data object used to create pictures (known as turtle graphics)