Purpose of constructors in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Python code using a constructor?

Consider this Python class with a constructor. What will be printed when the code runs?

Python

class Dog:
    def __init__(self, name):
        self.name = name

my_dog = Dog("Buddy")
print(my_dog.name)

A Buddy

B Dog object

C None

D Error: missing argument

💡 Hint

The constructor sets the name attribute when the object is created.

The __init__ method is the constructor. It sets the name attribute to 'Buddy'. So printing my_dog.name outputs 'Buddy'.

🧠 Conceptual

intermediate

What is the main purpose of a constructor in Python?

Choose the best description of what a constructor does in a Python class.

A It initializes new objects with default or given values.

B It deletes objects when they are no longer needed.

C It defines methods that can be called on objects.

D It creates new classes from existing ones.

💡 Hint

Think about what happens when you create a new object from a class.

A constructor (__init__) runs automatically when a new object is created. It sets up initial values for the object.

❓ Predict Output

advanced

What will this code print regarding constructor behavior?

Look at this Python code with a constructor and a method. What is the output?

Python

class Car:
    def __init__(self, brand):
        self.brand = brand

    def show_brand(self):
        print(f"Brand: {self.brand}")

car1 = Car("Toyota")
car1.show_brand()

A Error: show_brand missing argument

B Brand: car1

C Brand: None

D Brand: Toyota

💡 Hint

The constructor sets the brand attribute, which the method prints.

The constructor sets self.brand to 'Toyota'. The show_brand method prints it. So output is 'Brand: Toyota'.

🧠 Conceptual

advanced

Which statement about constructors is true?

Select the true statement about constructors in Python classes.

A Constructors can have any name you choose.

B Constructors run automatically when an object is created.

C Constructors must return a value.

D Constructors can only have one parameter.

💡 Hint

Think about when the __init__ method runs.

The constructor __init__ runs automatically when a new object is created. Its name must be __init__, it does not return a value, and it can have multiple parameters.

❓ Predict Output

expert

What is the output of this Python code with multiple constructors?

Python does not support multiple constructors by default. What will happen when this code runs?

Python

class Book:
    def __init__(self, title):
        self.title = title

    def __init__(self, title, author):
        self.title = title
        self.author = author

b = Book("1984")
print(b.title)

A None

B 1984

C Error: missing 1 required positional argument: 'author'

D Error: multiple constructors not allowed

💡 Hint

The second __init__ replaces the first one.

In Python, the second __init__ method overwrites the first. So Book expects two arguments. Calling Book("1984") with one argument causes a TypeError.