pythonpython-3.xdjangomongodbmotordriver

How to convert MotorLatentCommandCursor to list


I use Motor driver of mongoDB in my django project and I have problem to convert my data(who comes from database as cursor) to list, here is my code:

documents = db.factor.aggregate([{"$limit": 3},
     {"$lookup": {"from": "subfactor", "localField": "_id", "foreignField": "factor_id", "as": "subfactor"}}])

for d in await list(documents):
    print(d)

and the Error:

File "/usr/lib/python3.8/asyncio/runners.py", line 43, in run
return loop.run_until_complete(main)
File "/usr/lib/python3.8/asyncio/base_events.py", line 595, in run_until_complete
self.run_forever()
File "/usr/lib/python3.8/asyncio/base_events.py", line 563, in run_forever
self._run_once()
File "/usr/lib/python3.8/asyncio/base_events.py", line 1808, in _run_once
event_list = self._selector.select(timeout)
File "/usr/lib/python3.8/selectors.py", line 468, in select
fd_event_list = self._selector.poll(timeout, max_ev)

Solution

  • I don't know Motor but a quick check in their docs shows this:

    Cursor is async iterable, so you can use async for to iterate:

    async for document in db.test_collection.find({'i': {'$lt': 2}}):
        pprint.pprint(document)
    

    You can turn this into a list with a async list comprehention:

    items = [x async for x in db.test_collection.find({'i': {'$lt': 2}})]
    

    Also they have helper functions to convert a cursor to an awaitable list:

    items = await db.test_collection.find({'i': {'$lt': 2}}).to_list(length=100)