app.py

import requests

def refresh_access_token(refresh_token, client_id, client_secret, region="in"):
    token_url = f"https://accounts.zoho.{region}/oauth/v2/token"
    params = {
        "refresh_token": refresh_token,
        "client_id": client_id,
        "client_secret": client_secret,
        "grant_type": "refresh_token"
    }
    r = requests.post(token_url, params=params, timeout=20)
    r.raise_for_status()
    return r.json()["access_token"]