cancellable_task_group.md

cancellable task group

Language: Python · Sphere: programming · Category: Async

Signature: (name: str, duration: float, token: CancellationToken) → str

What it does

Async task group implementation with cancellation support.

Guarantee

When it runs, cancellable task group guarantees n_done == 3; len(results) == 3; t_quick.result == 'Task A finished instantly' (proven by run).

Checkable constraints:

• len(results) == 3
• t_quick.result == 'Task A finished instantly'
• t_quick.completed and t_quick.exception is None
• isinstance(t_fail.exception, ValueError)
• t_fail.result is None
• t_short.result == 'Task C completed successfully'
• n_done == 3
• tg.token.is_cancelled

Verification evidence

• Green-run: ✓ passes (re-run under the extractor's gate)
• Constraint strength: recovery (truth-pinned)
• Independent oracle: ✓ consensus — xlang (validator v1.9)
• Peer review: unreviewed

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