create/check data dir for arxiv's papers (#531)

examples/How_to_call_functions_for_knowledge_retrieval.ipynb

@@ -150,6 +150,8 @@
    "metadata": {},
    "outputs": [],
    "source": [
+    "import os\n",
+    "\n",
     "import arxiv\n",
     "import ast\n",
     "import concurrent\n",
@@ -190,6 +192,25 @@
    "id": "2de5d32d",
    "metadata": {},
    "outputs": [],
+   "source": [
+    "directory = './data/papers'\n",
+    "\n",
+    "# Check if the directory already exists\n",
+    "if not os.path.exists(directory):\n",
+    "    # If the directory doesn't exist, create it and any necessary intermediate directories\n",
+    "    os.makedirs(directory)\n",
+    "    print(f\"Directory '{directory}' created successfully.\")\n",
+    "else:\n",
+    "    # If the directory already exists, print a message indicating it\n",
+    "    print(f\"Directory '{directory}' already exists.\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "ae5cb7a1",
+   "metadata": {},
+   "outputs": [],
    "source": [
     "# Set a directory to store downloaded papers\n",
     "data_dir = os.path.join(os.curdir, \"data\", \"papers\")\n",
@@ -197,7 +218,7 @@
     "\n",
     "# Generate a blank dataframe where we can store downloaded files\n",
     "df = pd.DataFrame(list())\n",
-    "df.to_csv(paper_dir_filepath)\n"
+    "df.to_csv(paper_dir_filepath)"
    ]
   },
   {