15 Python Exception Handling Exercises and Examples

In Python programming, exceptions are events that occur during the execution of programs that disrupt the normal flow of instructions of the program. When an exceptional condition arises, Python raises an exception. If not handled, the program will crash. To prevent this, the exceptions are caught and handled using try, except, else, finally, and raise keywords.

In this post, I’ve put together some simple examples and exercises for handling exceptions in Python. Check out these examples to get a clear idea of how exception handling works in Python.

Let’s dive right in.

1. Basic try and except block

try:
    print(undefined_variable)
except NameError:
    print("This variable is not defined.")

Output:

2. Handling multiple exceptions

try:
    result = 10 / 0
except (ZeroDivisionError, TypeError) as e:
    print("Error occurred:", str(e))

Output:

3. Using the else clause in exception handling

try:
    result = 10 / 2
except ZeroDivisionError:
    print("Division by zero!")
else:
    print("Result is", result)

Output:

4. Using the finally clause in exception handling

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Division by zero!")
finally:
    print("This block of code will always execute.")

Output:

5. Raising exceptions using raise

try:
    raise ValueError("This is a custom error message.")
except ValueError as e:
    print("An error occurred:", str(e))

Output:

6. Creating custom exceptions

class CustomError(Exception):
    pass

try:
    raise CustomError("This is a custom error.")
except CustomError as e:
    print("An error occurred:", str(e))

Output:

7. Catching all exceptions using Exception

try:
    result = 10 / 0
except Exception as e:
    print("An error occurred:", str(e))
try:
    print(undefined_variable)
except Exception as e:
    print("An error occurred:", str(e))

Output:

8. Using assert for exception handling

try:
    x = -1
    assert x >= 0, "Only positive values are allowed."
except AssertionError as e:
    print("An error occurred:", str(e))

Output:

9. Handling exceptions within functions

def divide(a, b):
    try:
        return a / b
    except ZeroDivisionError:
        print("Division by zero!")
        return None

print(divide(10, 0))

Output:

10. Using a while loop for handling exceptions

while True:
    try:
        x = int(input("Please enter a number: "))
        break
    except ValueError:
        print("Oops! That was no valid number. Try again…")

Output:

11. Reraising exceptions

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Caught an exception")
    raise

Output:

12. Using else clause with try/except inside a function

def divide(a, b):
    try:
        result = a / b
    except ZeroDivisionError:
        print("Division by zero!")
        return None
    else:
        print("Division successful!")
        return result

print(divide(10, 2))

Output:

13. Handling exceptions with finally clause in file handling

try:
    f = open('myfile.txt', 'r')
    content = f.read()
    f.close()
except IOError:
    print('File not found.')

Output:

14. Ignoring exceptions

try:
    result = 10 / 0
except ZeroDivisionError:
    pass

Output: Prints nothing

15. Propagating exceptions

def sqrt(x):
    if x < 0:
        raise ValueError("Cannot compute square root of a negative number.")
    else:
        return x ** 0.5
    
try:
    print(sqrt(-10))
except ValueError as e:
    print("An error occurred:", str(e))

Output:

I hope this article helped you in understanding how exception handling works in Python. Always remember that proper exception handling makes your programs robust and easier to debug.

Check out my post on 18 Python Regular Expressions Exercises and Examples. Happy coding!