How to Return SSE Data in Python

Recently, I was using python to call the sse interface of gpt and return it to my front end through sse. I encountered a few problems, and I simply recorded them. There was no amount of code, but it took me more than half a day to get it done.

• how to return sse in python
• why do the newlines in the sse I return always get lost

import json
import time

from flask import Flask, request
from flask import Response, jsonify

app = Flask(__name__)

import openai
import time
import sys

openai.api_key = ''

@app.route('/stream', methods=["POST"])
def stream():
    messages = request.get_json()['messages']

    print(messages)
    response = openai.ChatCompletion.create(
        model='gpt-3.5-turbo',
        messages=messages,
        temperature=0.7,
        stream=True  # again, we set stream=True
    )
    def eventStream():
        id = 0
        for chunk in response:
            id += 1
            chunk_message = chunk['choices'][0]['delta']  # extract the message
            yield 'id: {}\nevent: message\ndata: {}\n\n'.format(id,json.dumps({'data': chunk_message.get('content', '')}))
        
        yield 'id: {}\nevent: close\ndata: {}\n\n'.format(id,json.dumps({'data': chunk_message.get('content', '')}))

    return Response(eventStream(), mimetype="text/event-stream")


if __name__  '__main__':
    app.run(host='0.0.0.0', port=8889)

There are several key points here, corresponding to the two questions at the beginning:

• The data type returned by the sse interface should be ‘“text/event-stream”’
• The returned data should be formatted ‘id: {}\ nevent: message\ ndata: {}\ n\ n’ .format (id, json.dumps ({‘data’: chunk_message ('content ', ‘’)}))`， This is the sse protocol. One newline character represents different data, two newlines represent a piece of data, and the id should not be repeated.
• data data is best returned with json string, the front end receives it and parses it again, even if your data is originally a string, otherwise you are likely to encounter the problem of missing newlines