from constants import OPENAI_API_KEY

!pip show langchain-openai | grep "Version:"

Version: 0.2.9

import os

os.environ["OPENAI_API_KEY"] = OPENAI_API_KEY

from langchain_openai import ChatOpenAI

model = ChatOpenAI(model="gpt-4o-mini")

from langchain_core.output_parsers import JsonOutputParser


async def _extract_country_names_streaming(input_stream):
    """A function that operates on input streams."""
    country_names_so_far = set()

    async for input in input_stream:
        if not isinstance(input, dict):
            continue

        if "countries" not in input:
            continue

        countries = input["countries"]

        if not isinstance(countries, list):
            continue

        for country in countries:
            name = country.get("name")
            if not name:
                continue
            if name not in country_names_so_far:
                yield name
                country_names_so_far.add(name)


chain = model | JsonOutputParser() | _extract_country_names_streaming

async for text in chain.astream(
    "output a list of the countries france, spain and japan and their populations in JSON format. "
    'Use a dict with an outer key of "countries" which contains a list of countries. '
    "Each country should have the key `name` and `population`",
):
    print(text, end="|", flush=True)

France|Spain|Japan|