What error is raised when a key or index cannot be found?

• A. TypeError
• B. KeyError
• C. LookupError
• D. ValueError

Answer: (C)

When a key or index cannot be found in a data structure, the error raised is typically a LookupError. This is a built-in exception in Python that serves as a base class for more specific lookup-related errors, which means it encompasses scenarios where key or index-based lookups fail. For instance, if you're trying to access a dictionary with a key that does not exist, a KeyError would be raised, which is a specific type of LookupError. Similarly, when working with sequences like lists, attempting to access an index that is out of range will raise an IndexError, also derived from LookupError.

Thus, LookupError is the most general category for issues like these, capturing the overarching problem of failing to retrieve a specific item based on a key or index. This clear hierarchy in exception handling allows for both broad error management (using LookupError) and specific cases that developers can catch individually (like KeyError or IndexError).