python runtime_error ai_generated true

asyncio.exceptions.CancelledError: CancelledError raised in task

ID: python/asyncio-task-cancellation-error

Also available as: JSON · Markdown · 中文
80%Fix Rate
86%Confidence
0Evidence
2025-06-15First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.8 active — — —
3.9 active — — —

Root Cause

A task was cancelled externally (e.g., via task.cancel()), and the cancellation was not handled, causing it to propagate.

generic

中文

任务被外部取消（例如通过 task.cancel()），且未处理取消操作，导致其传播。

Workarounds

  1. 90% success Catch CancelledError and perform cleanup, then re-raise 
    try:
    await long_running_coro()
except asyncio.CancelledError:
    # cleanup resources
    raise
  2. 85% success Use asyncio.shield() to protect critical sections 
    await asyncio.shield(critical_coro())

Dead Ends

Common approaches that don't work:

  1. Catching all exceptions except CancelledError 70% fail

    CancelledError is a subclass of BaseException, so it may not be caught by except Exception.

  2. Ignoring cancellation and continuing execution 50% fail

    The event loop may be shutting down, and ignoring cancellation can cause resource leaks or hangs.