diff --git a/02_end_to_end_machine_learning_project.ipynb b/02_end_to_end_machine_learning_project.ipynb
index a8386f5..41069f8 100644
--- a/02_end_to_end_machine_learning_project.ipynb
+++ b/02_end_to_end_machine_learning_project.ipynb
@@ -593,16 +593,35 @@
    "execution_count": 14,
    "metadata": {},
    "outputs": [],
+   "source": [
+    "from zlib import crc32\n",
+    "\n",
+    "def test_set_check(identifier, test_ratio):\n",
+    "    return crc32(np.int64(identifier)) & 0xffffffff < test_ratio * 2**32\n",
+    "\n",
+    "def split_train_test_by_id(data, test_ratio, id_column):\n",
+    "    ids = data[id_column]\n",
+    "    in_test_set = ids.apply(lambda id_: test_set_check(id_, test_ratio))\n",
+    "    return data.loc[~in_test_set], data.loc[in_test_set]"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "위의 `test_set_check()` 함수는 파이썬 2와 파이썬 3에서 모두 작동되고 다음의 hashlib를 사용한 구현보다 훨씬 빠릅니다."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "import hashlib\n",
     "\n",
-    "def test_set_check(identifier, test_ratio, hash):\n",
-    "    return hash(np.int64(identifier)).digest()[-1] < 256 * test_ratio\n",
-    "\n",
-    "def split_train_test_by_id(data, test_ratio, id_column, hash=hashlib.md5):\n",
-    "    ids = data[id_column]\n",
-    "    in_test_set = ids.apply(lambda id_: test_set_check(id_, test_ratio, hash))\n",
-    "    return data.loc[~in_test_set], data.loc[in_test_set]"
+    "def test_set_check(identifier, test_ratio, hash=hashlib.md5):\n",
+    "    return bytearray(hash(np.int64(identifier)).digest())[-1] < 256 * test_ratio"
    ]
   },
   {