Always Release the Lock

Medium ⏱ 12 min 53% acceptance ★★★★☆ 4.2

You are given a lock object with .acquire() and .release() methods and a task callable that might raise. Write run_locked(lock, task) that acquires, runs the task and returns its result — guaranteeing release() runs even when the task raises (let the exception propagate after releasing). finally is the tool.

Examples

Example 1

Input

run_locked(lock, lambda: 42)

Output

42 (lock released)

Explanation

On success and on failure alike, release() executes.

Constraints

Use try/finally.
Do not swallow the exception.

Topics

Exception Handlingfinally

Companies

Goldman SachsJPMorgan Chase

Hints

Hint 1

No except clause needed at all.

Hint 2

Code in finally runs on every exit path.

← Diagnose the Failure Type The Forgotten else of try →

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