diff --git a/pxutil/cli.py b/pxutil/cli.py
index 5f4ee37..b6e9138 100755
--- a/pxutil/cli.py
+++ b/pxutil/cli.py
@@ -57,16 +57,15 @@ def chat_main():
         description="ChatGPT cli, type q to exit. Set env variable OPENAI_API_KEY first."
     )
     parser.add_argument(
-        "--v4", action="store_true", help="use GPT-4-turbo, default is GPT-3.5-turbo"
+        "-m",
+        "--model",
+        default="gpt-3.5-turbo",
+        help="OpenAI chatGPT model, gpt-3.5-turbo (default), gpt-4o etc.",
     )
     args = parser.parse_args()
 
     register_signal_ctrl_c()
-    if args.v4:
-        model = "gpt-4-turbo"
-    else:
-        model = "gpt-3.5-turbo"
-    chat = ChatAPI(model=model)
+    chat = ChatAPI(model=args.model.strip())
     while True:
         question = input("> ")
         if question in ("q", "quit"):
@@ -128,4 +127,4 @@ def listmod_main():
     # sys.path.append(os.path.dirname(os.path.dirname(os.path.realpath(__file__))))
 
     # loop_main()
-    listmod_main()
+    chat_main()
diff --git a/pxutil/pxutil.py b/pxutil/pxutil.py
index 7738d95..1465a51 100755
--- a/pxutil/pxutil.py
+++ b/pxutil/pxutil.py
@@ -490,7 +490,7 @@ def grep(pattern, string=None, filename=None):
         return result
 
 
-def replace_in_file(files, old, new, backup=None):
+def replace_in_file(files, old, new, backup=""):
     """
     Replace in place directly on a file.
 
@@ -830,15 +830,15 @@ def chat(self, question: str):
         if isinstance(resp, Exception):
             return Exception("Chat API request failed with error: %s." % resp)
 
-        if len(resp["choices"]) >= 1:
-            for choice in resp["choices"]:
-                if choice["index"] == 0 and choice["finish_reason"] in ("stop", None):
-                    answer = choice["message"]["content"]
+        if len(resp["choices"]) >= 1:  # type: ignore
+            for choice in resp["choices"]:  # type: ignore
+                if choice["index"] == 0 and choice["finish_reason"] in ("stop", None):   # type: ignore
+                    answer = choice["message"]["content"]   # type: ignore
                     answer = answer.strip("\n").strip()
                     # record chat history
                     if self.remember_chat_history:
                         self.chat_history.append({"role": "user", "content": question})
-                        self.chat_history.append(choice["message"])
+                        self.chat_history.append(choice["message"])  # type: ignore
                     return answer
 
         return Exception(