Inheriting attributes and methods in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean to inherit attributes and methods in Python?

It means a new class (child) can use the properties (attributes) and actions (methods) of an existing class (parent) without rewriting them.

beginner

How do you define a child class that inherits from a parent class in Python?

You write the child class name followed by parentheses containing the parent class name, like: <code>class Child(Parent):</code>

beginner

If a child class does not have a method, but the parent class does, what happens when you call that method on a child object?

The child object uses the parent's method automatically because it inherits it.

intermediate

What is the purpose of the super() function in inheritance?

<code>super()</code> lets the child class call a method from its parent class, often to extend or reuse the parent's behavior.

beginner

Can a child class have its own attributes and methods different from the parent class?

Yes, a child class can add new attributes and methods or override existing ones from the parent.

How do you indicate that a class Dog inherits from a class Animal in Python?

A class Dog extends Animal:

B class Dog inherits Animal:

C class Dog -> Animal:

D class Dog(Animal):

In Python, inheritance is shown by putting the parent class name in parentheses after the child class name.

If a parent class has a method walk() and the child class does not, what happens when you call walk() on a child object?

A It uses the parent's <code>walk()</code> method.

B It causes an error because the child has no method.

C It does nothing.

D It calls a default method from Python.

The child inherits methods from the parent, so it uses the parent's walk() method.

What does the super() function do in a child class?

A Creates a new parent class.

B Calls a method from the parent class.

C Deletes the parent class.

D Overrides the parent class.

super() is used to call a method from the parent class inside the child class.

Can a child class have attributes that the parent class does not have?

A No, child classes must have the same attributes.

B Only if the parent allows it.

C Yes, child classes can add new attributes.

D Only if you use <code>super()</code>.

Child classes can add new attributes and methods beyond what the parent has.

Which of these is true about method overriding in inheritance?

A Child class can provide its own version of a parent's method.

B Parent class can override child's methods.

C Methods cannot be changed once inherited.

D Overriding deletes the parent's method.

Method overriding means the child class defines a method with the same name to replace the parent's version.

Explain in your own words what happens when a child class inherits from a parent class in Python.

Think about how a child can reuse and extend what the parent has.

Describe how and why you would use the super() function inside a child class method.

Imagine you want to add something extra but keep the parent's work.

Practice

1. What does it mean when a child class inherits from a parent class in Python?

easy

A. The child class must redefine all methods of the parent class to use them.

B. The child class can only use methods but not attributes of the parent class.

C. The child class automatically has all attributes and methods of the parent class.

D. The child class cannot add any new methods or attributes.

Solution

1. Step 1: Understand inheritance basics

   Inheritance means the child class gets all features (attributes and methods) of the parent class automatically.

2. Step 2: Analyze each option

   The child class automatically has all attributes and methods of the parent class. correctly states this. Options B, C, and D are incorrect because they limit or deny inheritance features.

3. Final Answer:

   The child class automatically has all attributes and methods of the parent class. -> Option C

4. Quick Check:

   Inheritance = automatic access to parent features [OK]

Hint: Inheritance means child gets all parent features automatically [OK]

Common Mistakes:

• Thinking child must redefine parent methods
• Believing child cannot add new features
• Assuming attributes are not inherited

2. Which of the following is the correct syntax to make class Dog inherit from class Animal in Python?

easy

A. class Dog(Animal):

B. class Dog -> Animal:

C. class Dog inherits Animal:

D. class Dog : Animal

Solution

1. Step 1: Recall Python inheritance syntax

   In Python, inheritance is shown by putting the parent class name in parentheses after the child class name.

2. Step 2: Match syntax to options

   class Dog(Animal): uses class Dog(Animal): which is correct. Others use invalid syntax.

3. Final Answer:

   class Dog(Animal): -> Option A

4. Quick Check:

   Inheritance syntax = class Child(Parent): [OK]

Hint: Use parentheses with parent class name after child class [OK]

Common Mistakes:

• Using 'inherits' keyword instead of parentheses
• Using arrow or colon incorrectly
• Omitting parentheses

3. What will be the output of this code?

class Parent:
    def greet(self):
        return "Hello from Parent"

class Child(Parent):
    pass

c = Child()
print(c.greet())

medium

A. Hello from Child

B. Hello from Parent

C. AttributeError

D. SyntaxError

Solution

1. Step 1: Understand method inheritance

   Child class inherits greet method from Parent because it has no own greet.

2. Step 2: Trace the method call

   Calling c.greet() runs Parent's greet returning "Hello from Parent".

3. Final Answer:

   Hello from Parent -> Option B

4. Quick Check:

   Inherited method runs if child has none [OK]

Hint: Child uses parent's method if not overridden [OK]

Common Mistakes:

• Expecting child's own greet method when none exists
• Confusing AttributeError with missing method
• Thinking syntax error occurs

4. Find the error in this code:

class Animal:
    def sound(self):
        return "Some sound"

class Dog(Animal):
    def sound():
        return "Bark"

d = Dog()
print(d.sound())

medium

A. print statement syntax error

B. Dog class should not inherit Animal

C. Cannot override methods in child class

D. Missing self parameter in Dog's sound method

Solution

1. Step 1: Check method definitions

   In Python, instance methods must have self as first parameter.

2. Step 2: Identify error in Dog's sound

   Dog's sound method lacks self, causing a TypeError when called on instance.

3. Final Answer:

   Missing self parameter in Dog's sound method -> Option D

4. Quick Check:

   Instance methods need self parameter [OK]

Hint: Always include self as first method parameter [OK]

Common Mistakes:

• Forgetting self in child method
• Thinking inheritance disallows overriding
• Assuming print syntax is wrong

5. Given these classes:

class Vehicle:
    def __init__(self, brand):
        self.brand = brand
    def info(self):
        return f"Vehicle brand: {self.brand}"

class Car(Vehicle):
    def __init__(self, brand, model):
        super().__init__(brand)
        self.model = model
    def info(self):
        return f"Car brand: {self.brand}, model: {self.model}"

What will print(Car('Toyota', 'Corolla').info()) output?

hard

A. Car brand: Toyota, model: Corolla

B. Vehicle brand: Toyota

C. Car brand: , model: Corolla

D. TypeError due to missing argument

Solution

1. Step 1: Understand constructor chaining

   Car's __init__ calls super().__init__(brand) to set brand in Vehicle.

2. Step 2: Analyze info method override

   Car overrides info to include both brand and model.

3. Step 3: Predict output

   Calling info() on Car instance returns "Car brand: Toyota, model: Corolla".

4. Final Answer:

   Car brand: Toyota, model: Corolla -> Option A

5. Quick Check:

   Child overrides method and calls parent's init [OK]

Hint: Use super() to inherit parent init, override methods as needed [OK]

Common Mistakes:

• Forgetting super() call in child __init__
• Expecting parent info output instead of child's
• Confusing missing arguments error