# RuntimeError: Cannot run the event loop while another loop is running

- **ID:** `python/asyncio-cannot-reenter-running-loop`
- **Domain:** python
- **Category:** runtime_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Calling loop.run_until_complete() or asyncio.run() from within a coroutine that is already executing on a running loop.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.7+ | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   async def outer():
    result = await inner_coro()  # no nested loop
   ```
2. **** (82% success)
   ```
   import asyncio, concurrent.futures
loop = asyncio.get_running_loop()
with concurrent.futures.ThreadPoolExecutor() as pool:
    result = await loop.run_in_executor(pool, lambda: asyncio.run(inner_coro()))
   ```

## Dead Ends

- **** — asyncio.run() refuses when a loop is already running and raises the same error. (90% fail)
- **** — Same restriction: you cannot nest loop runners on the same thread. (85% fail)