Which of these is the correct way to create a class-level exception?

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BlackTom AI · Accepted Answer

To determine the correct approach for creating a class-level exception, we should examine what each option actually does or defines.
Option 1: 'MyError = Exception()' assigns an instance of Exception to the name MyError. This does not define a new exception class; it simply creates an object, so it cannot be used as a type for raising or subclassing. This makes it incorrect for defining a new exception type.
Option 2: 'raise MyError' attempts to raise the name MyError. However, unless MyError has been defined as an exception class, this will fail. Even if MyError were defined as an instance or a non-exception object, raising it would be invalid. So this is not a correct way to define a class-level exception.
Option 3: 'class MyError: pass' defines a new class named MyError, but it does not inherit from Exception (or BaseException). In Python, to create a custom exception type, the class should subclass Exception. Without that inheritance, this is not a proper exception class, and will not behave as a standard exception.
Option 4: 'def MyError(Exception): pass' is syntactically invalid for defining a class. In Python, 'def' defines a function, not a class, and placing '(Exception)' after a function name is not valid syntax. This does not create an exception class.
Option 5: 'class MyError(Exception): pass' is the canonical and correct form. It defines a new class named MyError that inherits from Exception, making it a proper custom exception type that can be raised and caught like other exceptions. This aligns with Python’s exception hierarchy and standard practices for creating custom exceptions.
In summary, most options fail because they either attempt to assign instances, attempt to raise before proper definition, omit necessary inheritance from Exception, or misuse the def keyword. Only the final option correctly defines a new exception class by subclassing Exception.

IS 4485-001 Fall 2025 Final Exam Practice 2

Which of these is the correct way to create a class-level exception?

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