app.py

import streamlit as st
from langchain_openai import ChatOpenAI
from langchain.schema import AIMessage, HumanMessage, SystemMessage
import os

api_key = os.environ.get("OPENAI_API_KEY")
if not api_key:
    raise ValueError("OPENAI_API_KEY not found. Please set it in Hugging Face secrets.")

chat = ChatOpenAI(
    model="gpt-3.5-turbo",
    temperature=0,
    openai_api_key=api_key
)

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:
    st.session_state.sessionMessages = [
        SystemMessage(content="You are a helpful assistant.")
    ]

def load_answer(question):
    st.session_state.sessionMessages.append(HumanMessage(content=question))
    assistant_answer = chat.invoke(st.session_state.sessionMessages)
    st.session_state.sessionMessages.append(AIMessage(content=assistant_answer.content))
    return assistant_answer.content

user_input = st.text_input("You: ")
if st.button("Generate") and user_input:
    response = load_answer(user_input)
    st.subheader("Answer:")
    st.write(response)