20 Exception Handling Interview Questions and Answers

Exception Handling is a process of dealing with errors in a program. It is important for developers to have a strong understanding of Exception Handling in order to write quality code that can handle unexpected errors. During a job interview, you may be asked questions about Exception Handling in order to gauge your level of knowledge. In this article, we will review some common Exception Handling interview questions and provide tips on how to answer them.

Exception Handling Interview Questions and Answers

Here are 20 commonly asked Exception Handling interview questions and answers to prepare you for your interview:

1. What is an exception in Python?

An exception is an error that occurs during the execution of a program. Exceptions can be caused by a variety of things, such as division by zero or trying to access a list element that does not exist. When an exception occurs, the program will stop running and an error message will be displayed.

2. Can you explain the difference between errors and exceptions in Python?

Errors are generally caused by things that are out of our control, like hardware failures or syntax errors in our code. Exceptions, on the other hand, are things that we can anticipate and handle gracefully. For example, we can write code to catch a ValueError exception that might be raised if we try to convert a string to an int and the string can’t be parsed as a valid integer.

3. How do you handle exceptions in Python?

In Python, exceptions can be handled using the try-except statement. This statement allows you to catch errors and exceptions that might occur in your code, and then handle them accordingly. For example, you might use the try-except statement to catch an error and then print out a message to the user.

4. How can you ensure that a certain code block runs no matter whether there’s an exception or not?

You can use a finally block to ensure that a certain code block runs no matter what. A finally block will always execute, even if there is an exception.

5. Can you give me some examples of built-in exceptions in Python?

Some examples of built-in exceptions in Python include the following:

ImportError: An error that occurs when a module or dependency cannot be found.

ValueError: An error that occurs when a built-in operation or function receives an argument that has the right type but an inappropriate value.

KeyError: An error that occurs when a dictionary does not have a specific key.

IndexError: An error that occurs when a list or tuple is accessed with an index that is out of range.

6. When should you use assertions instead of try/except blocks?

Assertions should be used to check for conditions that should never occur in your code. For example, if you are working with a list, you might want to assert that the list is never empty. If an assertion fails, it will raise an exception. Try/except blocks, on the other hand, should be used to handle conditions that might occur in your code. For example, if you are trying to open a file, you might use a try/except block to handle the case where the file does not exist.

7. What are the best practices to follow when using try/except blocks?

There are a few best practices to follow when using try/except blocks:

1. Always specify a specific exception type rather than using a bare except: clause. This will prevent your code from accidentally catching unrelated exceptions.
2. Use a finally clause to clean up any resources that were used in the try block, regardless of whether an exception was raised or not.
3. When raising an exception, use a specific exception type rather than a generic Exception. This will make it easier for code that catches the exception to handle it appropriately.

8. How does the raise keyword work in Python?

The raise keyword is used to trigger an exception. When used without any arguments, it will re-raise the last exception that was raised. If you provide a value, it will be used as the exception.

9. How does the assert statement work in Python?

The assert statement is used to test a condition in Python. If the condition is True, then the program will continue to run. If the condition is False, then the program will stop running and an AssertionError will be raised.

10. What’s the difference between raising an error and throwing an exception in Python?

Raising an error will cause the program to stop running entirely. Throwing an exception will allow the program to continue running, but will generate an error message.

11. Is it possible for a finally clause to be executed even if an exception has occurred in the preceding try clause? If yes, then how?

Yes, it is possible for a finally clause to be executed even if an exception has occurred in the preceding try clause. This can happen if the exception is caught by an outer try block or if the thread of execution is terminated.

12. What do you understand about custom exceptions in Python?

In Python, a custom exception is a user-defined exception class. Custom exceptions are typically used to indicate errors that are specific to your application. For example, if you were developing a software application that needed to connect to a database, you might create a custom exception class to handle any errors that occur when connecting to the database.

13. What is your opinion on Python documentation standards? Are they sufficient?

I believe that the Python documentation standards are sufficient. They are clear and concise, and they provide enough information to be able to understand what is going on.

14. What are the differences between Java and Python exception handling mechanisms? Which one do you think is better?

The main difference between Java and Python exception handling mechanisms is that Java uses checked exceptions, while Python uses unchecked exceptions. Checked exceptions are those that the compiler checks for and forces the programmer to handle, while unchecked exceptions are those that the compiler does not check for. Python’s approach is generally considered to be better because it forces the programmer to deal with all possible errors, rather than just the ones that the compiler is aware of.

15. What is the advantage of using Python over Java with respect to exception handling?

Python’s advantage over Java when it comes to exception handling is that Python adopts a “batteries included” approach. This means that the language comes with a lot of built-in features and libraries, which makes it easier to get started with and develop programs. When it comes to exception handling, this means that Python has a richer set of tools for dealing with errors and exceptions. In contrast, Java takes a more minimalist approach, and as a result, exception handling can be more complex and require more boilerplate code.

16. Why is the else clause used in try/except blocks?

The else clause is used in try/except blocks in order to execute code if no exceptions are raised. This can be useful in situations where you want to perform some sort of cleanup after an operation, or where you want to provide alternative behavior if no errors occur.

17. What do you understand about the traceback module in Python?

The traceback module in Python is used for printing out a stack trace of an error that has occurred in your program. This can be helpful in debugging your code, as it can give you a clear idea of where the error occurred and what caused it.

18. What do you know about EAFP (Easier to Ask Forgiveness than Permission) programming style?

EAFP is a style of programming that is common in Python. It involves trying to execute a piece of code and catching any errors that occur. This is contrasted with the LBYL (Look Before You Leap) style, which involves checking for errors before trying to execute code. EAFP is often considered to be more Pythonic, as it is more in line with the Python philosophy of “we’re all adults here” and trusting programmers to handle errors as they occur.

19. How can you catch multiple exceptions at once in Python?

You can catch multiple exceptions at once by using a tuple of exception types in your except statement. For example:

try:
# some code
except (TypeError, ValueError):
# handle multiple exceptions
# TypeError and ValueError

20. What is the difference between the Exception class and the BaseException class in Python?

The Exception class is the most common type of exception that you will encounter in Python. It is used to indicate that an error has occurred, but it is not necessarily a fatal error. The BaseException class is the base class for all exceptions in Python. It is used to indicate that a more serious error has occurred, and it is usually a fatal error.