Custom error messages in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code with a custom error message?

Look at the code below. What will it print when run?

Python

def check_age(age):
    if age < 18:
        raise ValueError("Age must be at least 18")
    return "Access granted"

try:
    print(check_age(16))
except ValueError as e:
    print(e)

A Age must be at least 18

B Access granted

C ValueError

D TypeError

💡 Hint

The function raises an error if age is less than 18, and the error message is printed.

The function raises a ValueError with the message 'Age must be at least 18' when age is 16. The except block catches this and prints the message.

❓ Predict Output

intermediate

What error message is shown here?

What will this code print when run?

Python

def divide(a, b):
    if b == 0:
        raise ZeroDivisionError("Cannot divide by zero!")
    return a / b

try:
    print(divide(10, 0))
except ZeroDivisionError as e:
    print(e)

A Cannot divide by zero!

B None

C ZeroDivisionError

D division by zero

💡 Hint

The custom message inside the error is printed by the except block.

The function raises a ZeroDivisionError with the message 'Cannot divide by zero!' which is caught and printed.

❓ Predict Output

advanced

What is the output of this code with a custom exception class?

What will this code print when run?

Python

class MyError(Exception):
    def __init__(self, message):
        super().__init__(message)

try:
    raise MyError("Something went wrong!")
except MyError as e:
    print(f"Error: {e}")

A MyError

B Error: Something went wrong!

C Exception

D Something went wrong!

💡 Hint

The custom exception message is passed to the print statement with a prefix.

The custom exception MyError is raised with the message 'Something went wrong!'. The except block prints 'Error: ' plus the message.

❓ Predict Output

advanced

What error message is shown here with multiple exceptions?

What will this code print when run?

Python

def check_value(x):
    if x < 0:
        raise ValueError("Negative value not allowed")
    elif x == 0:
        raise ZeroDivisionError("Zero is not allowed")
    return x

try:
    check_value(0)
except ValueError as e:
    print(e)
except ZeroDivisionError as e:
    print(e)

A Negative value not allowed

B ZeroDivisionError

C ValueError

D Zero is not allowed

💡 Hint

The input is zero, so the ZeroDivisionError is raised and caught.

The function raises ZeroDivisionError with message 'Zero is not allowed' for input 0. The except block for ZeroDivisionError prints the message.

🧠 Conceptual

expert

Which option correctly defines a custom exception with a default message?

Choose the code that defines a custom exception class with a default error message that can be overridden.

A

class CustomError(Exception):
    message = "Default error message"
    def __init__(self, message):
        self.message = message

B

class CustomError(Exception):
    def __init__(self):
        self.message = "Default error message"
    def __str__(self):
        return self.message

C

class CustomError(Exception):
    def __init__(self, message="Default error message"):
        super().__init__(message)

D

class CustomError(Exception):
    def __init__(self, message):
        print(message)

💡 Hint

The correct class passes the message to the base Exception class and allows a default.

Option C correctly defines __init__ with a default message and calls super().__init__ to set it. This allows overriding the message or using the default.