Exceptions

Question 1

What are the two main types of errors in Python?

Answer 1

Syntax errors and exceptions.

Question 2

What is a syntax error in Python?

Answer 2

A parsing error indicating that code does not conform to Python’s grammatical rules.

Question 3

How does Python indicate the location of a syntax error?

Answer 3

Python outputs the offending line and character position, along with the file name and line number if applicable.

Question 4

What is an exception in Python?

Answer 4

An error detected during execution that does not necessarily stop the program and can be handled.

Question 5

What happens if an exception is not handled in Python?

Answer 5

The program displays an error message and typically halts execution.

Question 6

What information does the last line of a Python exception message provide?

Answer 6

It specifies the type of exception that occurred, such as ZeroDivisionError, NameError, or TypeError.

Question 7

Are standard exception names special keywords in Python?

Answer 7

No, they are built-in identifiers but not reserved keywords.

Question 8

What additional details does a Python exception message provide beyond the type?

Answer 8

It contains specific details based on the exception type and the cause.

Question 9

How does Python display the context of an exception?

Answer 9

Using a stack traceback that shows the sequence of code that led to the error.

Question 10

What section of Python documentation lists built-in exceptions and their meanings?

Answer 10

The Built-in Exceptions section.

Question 11

How can a Python program handle specific exceptions?

Answer 11

By using a try statement with except clauses for selected exceptions.

Question 12

What operations occur within a try statement in Python?

Answer 12

The try block runs; if no exception occurs, except is skipped, else it is executed if present.

Question 13

What happens if an exception occurs within the try block and matches an except clause?

Answer 13

The matching handler runs, and execution resumes after the try/except block.

Question 14

What does Python do if an exception is raised in the try block but does not match any except clause?

Answer 14

It passes the exception to outer try statements or stops execution with an error if unhandled.

Question 15

Can a try statement in Python have multiple except clauses?

Answer 15

Yes, to handle different exception types.

Question 16

How does Python determine which except handler to execute when multiple match?

Answer 16

Only the first matching handler is executed.

Question 17

What exceptions does a class named in an except clause match?

Answer 17

Exceptions that are instances of that class or its subclasses, but not base classes.

Question 18

How can a single except clause handle multiple exceptions in Python?

Answer 18

By specifying a parenthesized tuple of exception types.

Question 19

Can exception handlers capture exceptions that arise in called functions within the try block?

Answer 19

Yes, handlers process exceptions from functions called from the try block.

Question 20

How can a variable be assigned to a caught exception in except?

Answer 20

By specifying a variable after the exception type in the except statement.

Question 21

What attribute usually holds the arguments for an exception instance?

Answer 21

The .args attribute.

Question 22

How does the __str__() method of an exception relate to the error message?

Answer 22

Its output is shown as the final part of an unhandled exception message.

Question 23

What class is the base for all exceptions in Python?

Answer 23

BaseException.

Question 24

What is the base class for non-fatal exceptions

Answer 24

and which exceptions are usually not handled?

Question 25

Is it advisable to use Exception as a catch-all in except statements?

Answer 25

It works but being more specific is considered better practice.

Question 26

What is the typical pattern for handling and propagating exceptions?

Answer 26

Log or print the exception, then re-raise it to let callers handle it.

Question 27

What is the purpose of the else clause in a try…except statement?

Answer 27

To execute code if no exception was raised, reducing the risk of catching unrelated errors.

Question 28

Do exception handlers in a try block handle exceptions from functions called within the block?

Answer 28

Yes, exceptions from such functions are also handled.

Question 29

How can you force an exception to occur in Python?

Answer 29

By using the raise statement with an exception instance or exception class.

Question 30

How can you re-raise an exception without handling it?

Answer 30

By using raise without arguments.

Question 31

What happens when an exception occurs inside an except block?

Answer 31

The original exception is attached as context to the new exception.

Question 32

How does the ‘raise ... from ...’ syntax help with exceptions?

Answer 32

It explicitly sets the cause of a raised exception, clarifying exception chaining.

Question 33

How can you disable automatic exception chaining in Python?

Answer 33

By using from None with the raise statement.

Question 34

How are user-defined exceptions created in Python?

Answer 34

By defining a new class that inherits from Exception, directly or indirectly.

Question 35

What is the common naming convention for exception classes?

Answer 35

Exception class names usually end with 'Error'.

Question 36

How complex can a custom exception class be in Python?

Answer 36

It can be complex, but is usually simple with attributes for relevant information.

Question 37

Do Python standard modules define their own exceptions?

Answer 37

Yes, many modules define specific exception classes.

Question 38

What is the function of the finally clause in a try block?

Answer 38

To ensure clean-up code runs regardless of exceptions.

Question 39

When does the finally clause execute?

Answer 39

Always, upon completion of the try block, whether an exception occurred or not.

Question 40

What happens if both try and finally have return statements?

Answer 40

The value from the finally clause is returned.

Question 41

Why is the finally clause useful in real applications?

Answer 41

It reliably releases resources like files or network connections.

Question 42

What is the with statement used for in Python resource management?

Answer 42

It ensures predefined clean-up actions are performed, such as closing files.

Question 43

What does ExceptionGroup allow in Python 3.11+?

Answer 43

It wraps multiple unrelated exceptions to be raised and handled together.

Question 44

How can you handle specific exceptions within an ExceptionGroup?

Answer 44

By using except* to handle selected exception types in the group.

Question 45

What must be true about exceptions nested in an ExceptionGroup?

Answer 45

They must be exception instances, not types.

Question 46

How can you add contextual information to an exception after catching it?

Answer 46

By calling add_note(note) on the exception object.

Question 47

What is displayed in a traceback for an exception with notes?

Answer 47

All added notes are shown in traceback after the exception, in order added.

Question 48

How can contextual notes be useful with ExceptionGroup?

Answer 48

They help identify when and where each wrapped error occurred.