Add asyncio-threading/README.md

asyncio-threading/README.md

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+```python
+"""
+This gist shows how to run asyncio loop in a separate thread.
+It could be useful if you want to mix sync and async code together.
+Python 3.7+
+"""
+import asyncio
+from datetime import datetime
+from threading import Thread
+from typing import Tuple, List, Iterable
+
+import httpx
+
+URLS = [
+    "https://pypi.org",
+    "https://python.org",
+    "https://google.com",
+    "https://amazon.com",
+    "https://reddit.com",
+    "https://stackoverflow.com",
+    "https://ubuntu.com",
+    "https://github.com",
+    "https://microsoft.com",
+]
+
+
+def start_background_loop(loop: asyncio.AbstractEventLoop) -> None:
+    asyncio.set_event_loop(loop)
+    loop.run_forever()
+
+
+async def fetch(url: str) -> Tuple[str, int]:
+    """Does HTTP get on url and returns url and status code"""
+    async with httpx.AsyncClient() as session:
+        response = await session.get(url)
+        return url, response.status_code
+
+
+async def fetch_all_urls(urls: Iterable[str]) -> List[Tuple[str, int]]:
+    """Fetch all urls from the list of urls
+
+    It is done concurrently and combined into a single coroutine"""
+    tasks = [asyncio.create_task(fetch(url)) for url in urls]
+    results = await asyncio.gather(*tasks)
+    return results
+
+
+def main() -> None:
+    loop = asyncio.new_event_loop()
+    t = Thread(target=start_background_loop, args=(loop,), daemon=True)
+    t.start()
+
+    start_time = datetime.now()
+
+    task = asyncio.run_coroutine_threadsafe(fetch_all_urls(URLS), loop)
+    for url, status_code in task.result():
+        print(f"{url} -> {status_code}")
+
+    exec_time = (datetime.now() - start_time).total_seconds()
+    print(f"It took {exec_time:,.2f} seconds to run")
+    loop.stop()
+
+
+if __name__ == "__main__":
+    main()
+
+```
+CREDIT: https://gist.githubusercontent.com/dmfigol/3e7d5b84a16d076df02baa9f53271058/raw/dd7f9acf7afcc3c68b2b363d2e17ff6393dbde43/asyncio_loop_in_thread.py