Why Catch Order Matters

Hard ⏱ 18 min 30% acceptance ★★★★★ 4.8

LookupError is the parent of both KeyError and IndexError. Write lookup(container, key) that returns container[key] and classifies failures into 'key-miss' (KeyError), 'index-miss' (IndexError), or 'other-lookup' (any other LookupError) — and get the except order right, because putting the parent first would shadow the children.

Examples

Example 1

Input

lookup({'a': 1}, 'z')

Output

'key-miss'

Explanation

Dict lookups raise KeyError.

Example 2

Input

lookup([1, 2], 9)

Output

'index-miss'

Explanation

List lookups raise IndexError.

Constraints

Three except clauses, children before parent.
Return the value on success.

Topics

Exception Handlingexception hierarchy

Companies

MicrosoftAdobeOracle

Hints

Hint 1

Most-specific exceptions must come first.

Hint 2

The bare LookupError clause is the safety net.

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