from fastapi import FastAPI
from fastapi.responses import StreamingResponse
import io
import pandas as pd

app = FastAPI()

@app.get("/get_csv")
async def get_csv():
    df = pd.DataFrame(dict(col1 = 1, col2 = 2), index=[0])
    stream = io.StringIO()
    df.to_csv(stream, index = False)
    response = StreamingResponse(iter([stream.getvalue()]),
                                 media_type="text/csv"
                                )
    response.headers["Content-Disposition"] = "attachment; filename=export.csv"
    return response