error handling Flashcards
What is the base class for all exceptions in Python?
BaseException
What is the difference between BaseException and Exception?
BaseException is the top-level class for all exceptions (including system-exiting ones like SystemExit and KeyboardInterrupt). Exception is the base class for most non-fatal errors.
What does the try block do?
It contains code that might raise an exception.
What does an except block do?
It catches and handles a specific type of exception.
Can a try block have multiple except clauses?
Yes, a try block can have multiple except clauses for different exception types.
How do you catch multiple exceptions in a single except clause?
Use a tuple, e.g.: except (ValueError, TypeError):
What does except Exception as e: do?
It catches all exceptions that inherit from Exception. e stores the exception instance for further inspection.
What is the purpose of the else block in a try-except-else structure?
It runs only if no exception occurs in the try block.
What is the purpose of the finally block?
It always executes, whether or not an exception occurs.
When should you use a finally block?
To release resources (e.g., closing a file or database connection). To ensure cleanup, even if an exception occurs.
What happens if an exception is not caught by any except block?
The program crashes, and Python prints a traceback.
What happens if you raise an exception inside an except block?
The exception propagates further up the stack. If there’s no try-except higher up, the program crashes.
How do you manually raise an exception?
Use the raise keyword: raise ValueError(“Invalid input!”)
What does raise (without an exception type) do inside an except block?
It re-raises the caught exception.
What does assert do in Python?
It checks a condition and raises an AssertionError if false.
What happens if you place an except block for a parent exception before a child exception?
The parent catches everything first, so the child exception block never executes. Always put more specific exceptions before general ones.
How do you define a custom exception in Python?
Create a subclass of Exception: class MyError(Exception): pass
How do you access the message inside an exception?
Use .args or str(exception), e.g.: try: raise ValueError(“Something went wrong!”) except ValueError as e: print(e.args[0])
What is the difference between try-except and if-else for error handling?
try-except is for handling runtime errors (exceptions). if-else is for preventing errors before they occur.
What happens if a finally block contains return?
The finally block overrides any previous return statement.
