Lecture 7&8: Objects

Question 1

What is an object?

Answer 1

a collection of properties which can be expressed as variables and functions. With these components, an object can represent something.

Question 2

How do we call functions within an object?

Answer 2

methods

Question 3

How do we call variables within an object?

Answer 3

attributes

Question 4

What is a ‘class’?

Answer 4

a blueprint from which you can make objects. It defines what attributes and methods an object has.

Question 5

What is the ‘class constructor’ and how do you use this?

Answer 5

With the class constructor, the __init__ function is meant. It is used to create a new object of the type of class. The constructor creates a new variable following the blueprint; it is the builder/constructor.

class ClassName:
    def \_\_init\_\_(self):
        # Inside the class constructor
        # Code only runs when the object is first created

Question 6

What does the ‘self.’ keyword mean? What is it relevance? When must it be used?

Answer 6

self. refers to the object it is used on.
!You need to add this to every method you want to use in a particular class!

e.g.:
class Robot:
    def \_\_init\_\_(self, name, colour, age):
        self.n = name
        self.c = colour
        self.a = age

    def introduce_self(self):
        return("My name is " + self.n)

robot_1 = Robot(“Tom”, “Purple”, 19)

print(robot_1.introduce_self())

> “My name is Tom”

Question 7

What are the internal variables? What are the external variables? What is the fundamental difference between these two?

Use this example: 
class Robot:
    def \_\_init\_\_(self, name, colour, age):
        self.n = name
        self.c = colour
        self.a = age

    def introduce_self(self):
        return("My name is " + self.n)

robot_1 = Robot(“Tom”, “Purple”, 19)

print(robot_1.introduce_self())

> “My name is Tom”

Answer 7

Internal variables can be whatever you want. When using setters, you change the internal variables.
> in the example, the internal variables are ‘n’, ‘c’ and ‘a’.

External variables are fixed; they cannot be changed.
> in the example, the external variables are ‘name’, ‘colour’ and ‘age’.

Question 8

What are ‘arguments’?

Answer 8

The variables used within the class constructor (__init__).

e.g. 
class Robot:
    def \_\_init\_\_(self, name, colour, age):
        self.n = name
        self.c = colour
        self.a = age