Exception hierarchy in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of exception handling with hierarchy

What is the output of this code snippet?

Python

class MyError(Exception):
    pass

class MySubError(MyError):
    pass

try:
    raise MySubError("Oops")
except MyError:
    print("Caught MyError")
except Exception:
    print("Caught Exception")

A No output

B Caught Exception

C RuntimeError

D Caught MyError

💡 Hint

Remember that catching a base exception also catches its subclasses.

MySubError is a subclass of MyError, so the first except block catches it and prints 'Caught MyError'.

❓ Predict Output

intermediate

Exception hierarchy and multiple except blocks

What will be printed when this code runs?

Python

try:
    raise KeyError('key')
except LookupError:
    print('Caught LookupError')
except KeyError:
    print('Caught KeyError')

A Caught LookupError

B Caught KeyError

C No output

D KeyError not caught

💡 Hint

Check the order of except blocks and exception inheritance.

KeyError is a subclass of LookupError. The first except block matches and runs, so 'Caught LookupError' is printed.

❓ Predict Output

advanced

Output of exception chaining with hierarchy

What is the output of this code?

Python

class BaseError(Exception):
    pass

class DerivedError(BaseError):
    pass

try:
    try:
        raise DerivedError('inner')
    except DerivedError as e:
        raise BaseError('outer') from e
except BaseError as e:
    print(type(e).__name__)
    print(type(e.__cause__).__name__)

A DerivedError\nDerivedError

B BaseError\nBaseError

C BaseError\nDerivedError

D DerivedError\nBaseError

💡 Hint

Look at the exception chaining with 'from' keyword.

The outer exception is BaseError, and its cause is the inner DerivedError exception.

❓ Predict Output

advanced

Exception hierarchy and catching order

What will this code print?

Python

class A(Exception):
    pass

class B(A):
    pass

class C(B):
    pass

try:
    raise C()
except B:
    print('Caught B')
except A:
    print('Caught A')

A Caught B

B Caught A

C No output

D RuntimeError

💡 Hint

The first matching except block is executed.

C is subclass of B, so except B catches it first and prints 'Caught B'.

🧠 Conceptual

expert

Identify the base class of all built-in exceptions

Which class is the base class for all built-in exceptions in Python?

A Exception

B BaseException

C StandardError

D Error

💡 Hint

This class is the root of the exception hierarchy and includes system-exiting exceptions.

BaseException is the root class for all exceptions, including system-exiting ones like SystemExit and KeyboardInterrupt.