app.py

#
import streamlit as st

# import openai from langchain_openai
from langchain_openai import ChatOpenAI

# import HumanMessage,SystemMessage and AIMessage from the 'schema' module of the 'langchain' library.
from langchain.schema import (
    AIMessage,
    HumanMessage,
    SystemMessage
)

# From here down is all the StreamLit UI
st.set_page_config(page_title="LangChain Demo", page_icon=":robot:")
st.header("Hey, I'm your Chat GPT")


# If "sessionMessages" not in st.session_state, then create a list of SystemMessage
if "sessionMessages" not in st.session_state:
     st.session_state.sessionMessages = [
        SystemMessage(content="You are a helpful assistant.")
    ]


def load_answer(question):
    # Append the question to the sessionMessages list
    st.session_state.sessionMessages.append(HumanMessage(content=question))

    # Invoke the chat with the sessionMessages list
    assistant_answer  = chat.invoke(st.session_state.sessionMessages )

    # Append the assistant's answer to the sessionMessages list
    st.session_state.sessionMessages.append(AIMessage(content=assistant_answer.content))

    # Return the assistant's answer
    return assistant_answer.content


def get_text():

    # Get the user input
    input_text = st.text_input("You: ")
    return input_text

# Initialize the ChatOpenAI object
chat = ChatOpenAI(temperature=0)

# Get user input
user_input=get_text()

# Add button to generate response
submit = st.button('Generate')  

if submit:
    # Get response from the user input and display it
    response = load_answer(user_input)
    st.subheader("Answer:")

    st.write(response)