Chapter 4 - Definitions

Question 1

Define attribute

Answer 1

Some state or value that belongs to a particular object. For example, tess has a colour.

Question 2

Define canvas

Answer 2

A surface within a window where drawing takes place

Question 3

Define control flow

Answer 3

See “flow of execution” in the next chapter

Question 4

Define for loop

Answer 4

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

Question 5

Define instance

Answer 5

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

Question 6

Define invoke

Answer 6

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 7

Define iteration

Answer 7

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

Question 8

Define 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

Define method

Answer 9

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 10

Define module

Answer 10

A file containing Python definitions and statements intended for use in other Python programs. The contents of a module are made available to the other program by using the import statement.

Question 11

Define object

Answer 11

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

Question 12

Define range

Answer 12

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

Question 13

Define sequential

Answer 13

The default behaviour of a program. Step by step processing of algorithm.

Question 14

Define state

Answer 14

The collection of attribute values that a specific data object maintains

Question 15

Define terminating condition

Answer 15

A condition that occurs which causes a loop to stop repeating its body. In the for loops we saw in this chapter, the terminating condition has been when there are no elements to assign to the loop variable

Question 16

Define turtle

Answer 16

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