What is the asyncio.to_thread function?

Question

Accepted Answer

**asyncio.to_thread** runs **blocking functions** in a separate thread.

```python
import asyncio
import time

# Blocking function
def blocking_io():
    time.sleep(2)  # Simulate blocking I/O
    return "Data from disk"

def cpu_bound():
    return sum(i * i for i in range(10**7))

async def main():
    # Run blocking functions without blocking event loop
    result = await asyncio.to_thread(blocking_io)
    print(result)

# With arguments
    result = await asyncio.to_thread(cpu_bound)
    print(result)

# Multiple threads
    results = await asyncio.gather(
        asyncio.to_thread(blocking_io),
        asyncio.to_thread(blocking_io),
    )
    print(results)  # Runs concurrently

asyncio.run(main())
```

**vs run_in_executor:**
- `to_thread` is simpler (no executor needed).
- `run_in_executor` gives more control.

**Use cases:**
- File I/O in async code.
- CPU-bound tasks in async context.
- Wrapping blocking libraries.

Python: What is the asyncio.to_thread function?