python runtime_error ai_generated true

asyncio.exceptions.CancelledError: Task was cancelled

ID: python/asyncio-task-cancellation-not-handled

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2024-03-22First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.8 active — — —
3.9 active — — —
3.10 active — — —

Root Cause

A coroutine that is cancelled while awaiting an operation does not handle CancelledError, causing the task to terminate abruptly and potentially leaving resources unclean.

generic

中文

协程在等待操作时被取消，但未处理 CancelledError，导致任务突然终止并可能使资源未清理。

Workarounds

  1. 95% success 
    try:
    await long_operation()
except asyncio.CancelledError:
    # cleanup resources
    raise  # re-raise to acknowledge cancellation
  2. 80% success 
    result = await asyncio.shield(critical_operation())

Dead Ends

Common approaches that don't work:

  1. 70% fail

    Ignoring cancellation can violate asyncio's cooperative cancellation model and lead to tasks that never truly cancel.

  2. 40% fail

    Finally runs but the exception propagates; if not caught, it may still terminate the task.