← VCE Software Development U4O1

Public attributes and methods

A public member has no leading underscore, so code inside or outside the class can access it, e.g. self.name in the class or pet.name outside it.

Part of: VCE Software Development - U4O1 - development and evaluation — Module 76

Understanding Public attributes and methods in VCE Software Development U4O1

What it does: A public attribute like name can be accessed from outside the class with object.attribute. The leading underscore marks a member as protected by convention. With no underscore, speak is public. Inside the class, attributes are reached through self. A bare age would be an undefined variable.

Common mistakes: Without self., this only sets a local variable, so no public attribute is created. It should be self.name = name so pet.name works outside the class. Every method needs self as its first parameter so it can use self.name. It should be def speak(self):.

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This module's key terms are also in a printable crossword (Modules 3–79) and word search (Modules 3–114).

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Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

Which attribute is public?

self.nameself._name

Matches

self._name = name # meant to be public

↓

The leading underscore makes the attribute protected by convention, not public. Use self.name to make it public.

Applying

Meanings

Term

self.name

Meaning

A public member has no leading underscore, so code inside or outside the class can access it, e.g. self.name in the class or pet.name outside it.

Practice

class Pet:

Testing

Gaps

pet.()

Check Answer

Spots

2 def __init__(self, name):

3 name = name

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Quick Questions

1. Which attribute is public?

A. self._name

B. self.name ✓

A public attribute has no leading underscore, so code inside or outside the class can use it.

2. Which line reads a public attribute from outside the class (pet is an object)?

A. print(pet.name) ✓

B. print(self.name)

Outside the class there is no self. You use the object's name, such as pet.name.

3. True or false: a public method can be called from outside the class, e.g. pet.speak().

A. True ✓

B. False

Public methods have no leading underscore and can be called from anywhere, including outside the class.

4. Which method name is public?

A. def speak(self): ✓

B. def _speak(self):

The leading underscore marks a member as protected by convention. With no underscore, speak is public.

5. Which line changes a public attribute from outside the class?

A. self.name = 'Rex'

B. pet.name = 'Rex' ✓

Outside the class you use the object variable (pet.name). self only works inside the class's methods.

Match the Pairs

self.name = name → Creates a public attribute with no leading underscore, so any code can read or change it

def speak(self): → Defines a public method that can be called from inside or outside the class

Code outside the class can read a public attribute using the object name and a dot → print(pet.name)

Code outside the class can call a public method on an object → pet.speak()

self._name = name # meant to be public → The leading underscore makes the attribute protected by convention, not public. Use self.name to make it public.

print(name) # outside the class → The attribute is accessed without an object. Outside the class a public attribute needs the object and a dot, like pet.name.

Key Term

self.name

A public member has no leading underscore, so code inside or outside the class can access it, e.g. self.name in the class or pet.name outside it.

Fill in the Blanks

1. pet = Pet("Milo") pet.speak() print(pet.name)

Hint: Type the name of the public method that is called from outside the class to make the pet bark.

2. pet = Pet("Milo") print(pet.name)

Hint: Type the object variable used to reach the public attribute from outside the class.

3. class Pet: def speak(self): print("Woof!")

Hint: Type the first parameter that every public method receives so it can refer to its own object.

4. def intro(self): self.speak()

Hint: Type the keyword that refers to the current object when one method calls another inside the class.

5. pet = Pet("Milo") print(pet.name) pet.speak()

Hint: Type the class name used to create the object, so its public members can be used outside the class.

Spot the Error

Question 1

A class Pet:

B def __init__(self, name):

C name = name

D pet = Pet("Rex")

E print(pet.name)

Line C — Without self., this only sets a local variable, so no public attribute is created. It should be self.name = name so pet.name works outside the class.

Question 2

A class Pet:

B def __init__(self, name):

C self.name = name

D def speak():

E print(self.name, "woofs")

F Pet("Rex").speak()

Line D — Every method needs self as its first parameter so it can use self.name. It should be def speak(self):.

Question 3

A class Dog:

B def _bark(self):

C print("Woof!")

D rex = Dog()

E rex.bark()

Line B — The leading underscore means the method is not public, so rex.bark() fails from outside the class. A public method has no underscore: def bark(self):.

Question 4

A class Car:

B def __init__(self, make)

C self.make = make

D car = Car("Kia")

E print(car.make)

Line B — The def line is missing its colon. It should be def __init__(self, make): so the public attribute self.make can be set.

Question 5

A class Player:

B def __init__(self):

C self.__score = 0

D p = Player()

E print(p.score)

Line C — The double underscore makes score private, so p.score fails outside the class. A public attribute has no leading underscore: self.score = 0.

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