Quick Fix: To transition from OpenAI to ChatOpenAI in your Langchain and Flask setup, start by setting the "OPENAI_API_KEY" environment variable to an empty string. Utilize the ChatOpenAI class from Langchain. Introduce a generator class to handle streaming, and instantiate a ChatOpenAI object with the appropriate parameters. Initiate a thread to handle the conversational flow and return the generator as the Flask response.
The Problem:
How can I change the implementation from OpenAI to ChatOpenAI in a Flask application that uses LangChain for streaming responses from the OpenAI server?
The Solutions:
Solution 1: Implementing ChatOpenAI in Langchain and Flask
To replace OpenAI with ChatOpenAI in your Langchain and Flask implementation, follow these steps:
Import Necessary Libraries:
Import the ChatOpenAI model from langchain.chat_models.
Import the StreamingStdOutCallbackHandler from langchain.callbacks.streaming_stdout.
Define the Threaded Generator:
Create a ThreadedGenerator similar to the original implementation, which allows communication between the Flask app and the ChatOpenAI thread.
Define the Chain Stream Handler:
Create a ChainStreamHandler similar to the original implementation, but change the base class to StreamingStdOutCallbackHandler.
Define the llm_thread Function:
Create an llm_thread function similar to the original implementation, but use ChatOpenAI instead of OpenAI. The chat method takes a list of messages as input, so you’ll need to wrap your prompt in a list.
Define the Chain Function:
Create a chain function similar to the original implementation, which starts a thread to run the llm_thread function and returns the threaded generator.
Update the POST Route:
Update the chain route in your Flask app to handle POST requests. The request should receive a JSON object with a prompt key containing the user’s prompt.
Update the index Route:
Update the index route in your Flask app to use the updated HTML template. The template will remain largely the same, but you may need to update some IDs or class names if necessary.
By following these steps, you can successfully replace OpenAI with ChatOpenAI in your Langchain and Flask implementation, allowing you to stream responses from ChatOpenAI in your web application.
Solution 2: Fix “on_chat_model_start” Method
To resolve the error in your code when switching from OpenAI to ChatOpenAI, you need to modify the on_chat_model_start method in the ChainStreamHandler class. In the original code, this method only prints "started" when the chat model starts. However, in the updated version, the on_chat_model_start method expects two additional parameters: serialized and messages. The serialized parameter is a dictionary containing information about the chat model, and messages is a list of lists of base messages.
By making this change, you’ll adhere to the updated requirements of the on_chat_model_start method in the ChatOpenAI library. This should resolve the error you were encountering and allow you to successfully stream responses from ChatOpenAI in your Flask application.
Remember to replace the old on_chat_model_start method with the corrected one in your code.
Q&A
In Langchain and Flask, how can the OpenAI library be replaced with ChatOpenAI?
—
Import the ChatOpenAI class from the langchain.chat_models module and use it instead of the OpenAI class.
What changes are necessary in the streaming callback handler to work with ChatOpenAI?
—
In the streaming callback handler, change the on_llm_new_token method to send the token to the generator.
How can ChatOpenAI be called to generate text using the modified code?
—
Create a ChatOpenAI instance, set its parameters, and call it with a list of HumanMessage objects as input.
Video Explanation:
The following video, titled "Code an OpenAI integration with Python and Flask - YouTube", provides additional insights and in-depth exploration related to the topics discussed in this post.
... OpenAI & LangChain in 14 minutes Credits includes... - OpenAI - LangChain ... Go to channel · Chat with Multiple PDFs | LangChain App Tutorial in ...
