TypeError: object of type 'Cursor' has no len()

Starting Mongo 4.0.3/PyMongo 3.7.0, you could alternatively use count_documents instead of count on a cursor:

db.collection.count_documents({ "a": 2 })
# where { "a": 2 } is whatever filtering query

db.collection.count_documents is the alternative to the now deprecated db.collection.count.

Yes, count will do the work for you.

length = reply.count() 

or

length = reply.count(with_limit_and_skip=False)

had to suffer a lot coz length = count(reply) also did not work. Since I'm not allowed to comment yet, thought to leave this answer. Hope this will help somebody to save some time.

The pymongo cursor has a method count() which will return what you're looking for:

reply = db['test'].find(
  {"date":{"$gt":date_query}},
  {"date":1,"route_id":1,"loc":1,"_id":0}
)

length = reply.count()