Classes and objects in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a class in Python?

A class is a blueprint or template for creating objects. It defines properties (attributes) and behaviors (methods) that the objects created from it will have.

beginner

What is an object in Python?

An object is an instance of a class. It is a specific example created using the class blueprint, holding actual data and able to perform actions defined by the class.

beginner

What is the purpose of the __init__ method in a class?

The __init__ method is a special function called a constructor. It runs automatically when a new object is created and is used to set up initial values for the object's attributes.

beginner

How do you create an object from a class named Car?

You create an object by calling the class name like a function. For example: <code>my_car = Car()</code> creates an object named my_car from the Car class.

intermediate

What is the difference between a class attribute and an instance attribute?

A class attribute is shared by all objects of the class. An instance attribute is unique to each object and usually set inside the __init__ method.

What keyword is used to define a class in Python?

A object

B class

C def

D func

The keyword class is used to define a new class in Python.

Which method is automatically called when creating a new object?

A __init__

B __str__

C __call__

D __new__

The __init__ method runs automatically to initialize a new object.

How do you access an object's attribute named 'color'?

A color.object

B object->color

C object[color]

D object.color

Use dot notation like object.color to access an attribute.

What is the output of this code? class Dog: def __init__(self, name): self.name = name my_dog = Dog('Buddy') print(my_dog.name)

A Buddy

B name

C Dog

D Error

The object my_dog has the attribute name set to 'Buddy', so printing it shows 'Buddy'.

Which of these is true about instance methods?

A They can only access class attributes.

B They cannot modify object data.

C They must have 'self' as the first parameter.

D They are called without creating an object.

Instance methods always have 'self' as the first parameter to access the object's data.

Explain in your own words what a class and an object are, and how they relate.

Think about how a cookie cutter (class) makes cookies (objects).

Describe the role of the __init__ method and why it is important when creating objects.

It's like setting up your new phone with your name and settings right after buying it.