Object Is Not JSON Serializable When Using JSON Dumps

I am using an async method to return an array of objects and I am getting a "TypeError: is not JSON serializable" error and I am not sure how to correct it. Here is my code:

async def fetch(session, url):
    async with session.get(url) as response:
        return await response.text

class NewStoriesHandler(tornado.web.RequestHandler):
    async def get(self):
        self.set_header("Access-Control-Allow-Origin", "*")
        response = requests.get(
        "https://hacker-news.firebaseio.com/v0/newstories.json?print=pretty")
        data = response.json()
        story_list = []
        async with aiohttp.ClientSession() as session:
           for url in data:
               story_list.append(fetch(session, url))

        print(story_list)
        self.write(json.dumps(story_list, default=json_util.default))
        self.finish()

I tried to return Json back to the method but it was unsuccessful and I not sure what it is expecting back. The loop return an object for each call and appends it to the array.

Solution

it looks to me like you are adding co-routine objects to the list, rather than the results of the coroutines.

i think you should await each fetch before adding them to the list. I haven’t been able to run the code because i’m currently traveling, but you probably also need a strategy to start each task’s execution before you await it.