From 208ff34306bdc72974713e637494bb86fec8d6cb Mon Sep 17 00:00:00 2001
From: teihenn <hm.hr.yossy@gmail.com>
Date: Mon, 13 Jan 2025 14:50:01 +0900
Subject: [PATCH] docs: Add a comment for extract_alphanumeric

---
 src/basic/string.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/basic/string.py b/src/basic/string.py
index c69b706..eb5b4c1 100644
--- a/src/basic/string.py
+++ b/src/basic/string.py
@@ -38,6 +38,7 @@ def extract_alphanumeric(s: str) -> str:
         >>> extract_alphanumeric("こんにちは123ABCワールド")
         '123ABC'
     """
+    # isalnum() alone would include Unicode alphanumeric characters (like '１２３４５' or 'ＡＢＣＤＥ')
     # isascii() ensures we only get ASCII characters (0-127),
     # excluding Unicode characters like Japanese, Emoji, etc.
     return "".join(c for c in s if c.isascii() and c.isalnum())