Update app.py

app.py

@@ -9,14 +9,13 @@ st.title("💬 Chatbot")
 st.caption("")
 
 # Initialize session state for storing messages if it doesn't already exist
-
+if "messages" not in st.session_state:
+    st.session_state["messages"] = [{"role": "assistant", "content": "How can I help you?"}]
 
 # Display all previous messages
 for msg in st.session_state.messages:
     st.chat_message(msg["role"]).write(msg["content"])
 
-# Select model using a dropdown
-model_choice = st.selectbox('Choose a model:', ['gpt-3.5-turbo', 'gpt-4-turbo'])
 
 # Input for new prompts
 prompt = st.chat_input("Enter your question:")
@@ -38,3 +37,6 @@ if prompt:
     # Append and display the assistant's response
     st.session_state.messages.append({"role": "assistant", "content": msg})
     st.chat_message("assistant").write(msg)
+
+    # Select model using a dropdown
+    model_choice = st.selectbox('Choose a model:', ['gpt-3.5-turbo', 'gpt-4-turbo'])