What is the difference between asyncio and threading?

Question

Accepted Answer

**asyncio** — single-threaded concurrency. **threading** — multi-threaded parallelism.

```python
import asyncio
import threading
import time

# asyncio — single thread, cooperative
async def async_fetch(url):
    await asyncio.sleep(1)  # Yields control
    return f"Data from {url}"

async def async_main():
    tasks = [async_fetch(f"url{i}") for i in range(5)]
    return await asyncio.gather(*tasks)

# threading — multiple threads, preemptive
def thread_fetch(url):
    time.sleep(1)  # Blocks thread, GIL released
    return f"Data from {url}"

def thread_main():
    threads = [
        threading.Thread(target=thread_fetch, args=(f"url{i}",))
        for i in range(5)
    ]
    for t in threads:
        t.start()
    for t in threads:
        t.join()
```

**Comparison:**
- **asyncio**: lower overhead, explicit awaiting, no race conditions.
- **threading**: simpler for blocking libs, OS-managed scheduling.
- **asyncio** better for 1000+ concurrent connections.
- **threading** better when using blocking libraries.

Python: What is the difference between asyncio and threading?