--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/async_multi_threads/async.py	Thu Dec 25 20:07:46 2025 -0800
@@ -0,0 +1,48 @@
+
+# 1. asynciously down list of urls
+# 2. retries
+
+
+
+import asyncio
+from concurrent.futures import ThreadPoolExecutor
+import random
+from typing import List
+import time
+
+async def interface_download_url(url: str, retry_number = 0):
+    curr = time.time()
+    success = False
+    try:
+        res = await func_download_url(url)
+        success = True
+    except:
+        res = await interface_download_url(url, retry_number + 1)
+        res = None
+    long = curr - time.time()
+    return success, res, url, long
+    
+async def func_download_url(url: str):
+    await asyncio.sleep(random.randint(1, 10))
+
+ALLOWED_BATCH_SIZE = 10
+ALLOWED_RETRY_SIZE = 3
+async def download_multi_urls(urls: List[str], retry_num = 0):
+    if retry_num > ALLOWED_RETRY_SIZE:
+        return
+
+    number_of_batch = len(urls) // ALLOWED_BATCH_SIZE + 1
+
+    errors = []
+    for batch_num in range(number_of_batch):
+        download_urls = urls[batch_num * ALLOWED_BATCH_SIZE:(batch_num + 1) * ALLOWED_BATCH_SIZE]
+        for download_url in download_urls:
+            asyncio.run(asyncio.create_task(interface_download_url(download_url)))
+        results = await asyncio.gather(*tasks)
+        for task in tasks
+        asyncio.run()
+        for result in results:
+            if not result[0]:
+                errors.append(result[2])
+
+    await download_multi_urls(errors, retry_num+1)