使用pymongo的字段选择的mongodb的最后一条记录

Question

I have a mongo collection with the fields: _id, id_station and last_date_tx (this it is a datetime). I need to extract the last _id according an assigned id_station. This code:

tx = collectiondate.find({'id_station': "2052"}, {'_id': -1}).limit(1)
print(tx)

for pp in tx:
   print(tx)
   datetime_tx = pp['last_date_tx']
print(datetime_tx)

it produces the error:

<pymongo.cursor.Cursor object at 0x0000026841E64970>
{'_id': ObjectId('60fad1f65f26c6c04b59bd98')}
---------------------------------------------------------------------------
KeyError                                  
Traceback (most recent call last)
<ipython-input-33-86c8682bca23> in <module>
  4 for pp in pippo:
  5     print(pp)
----> 6     datetime_tx = pp['last_date_tx']
  7 print(datetime_tx)

KeyError: 'last_date_tx'

Any solution found doesn't solve my problem. Thanks for your help.

Answer 1

您可以使用find_one并以这种方式sort ：

tx = collectiondate.find_one({'id_station': "2052"}, sort=[( 'last_date_tx', pymongo.DESCENDING )])