How make a correct query from pymongo - mongodb

Question

I am using pymongo to subset a collection in mongodb, I am having problems with the syntax of the query, this is my query:
import pymongo
client=pymongo.MongoClient("localhost",27017)
db=client("publications")
collec=db("zikaVirus2")
pipeline=db.collec.aggregate([
{"$match":{"fullText":{"$exists": "true"}}},
{"$out": "pub_fulltext"}
])
db.pub_fulltext.aggregate(pipeline)
I am getting this error:
Traceback (most recent call last):
File "genColFulltext.py", line 3, in <module>
db=client("publications")
TypeError: 'MongoClient' object is not callable
UPDATE 1
If I do
import pymongo
client=pymongo.MongoClient("localhost",27017)
db=client.publications
collec=db.zikaVirus2
pipeline=db.collec.aggregate([
{"$match":{"fullText":{"$exists": "true"}}},
{"$out": "pub_fulltext"}
])
db.pub_fulltext.aggregate(pipeline)
I get
Traceback (most recent call last):
File "genColFulltext.py", line 11, in <module>
db.pub_fulltext.aggregate(pipeline)
File "/home/danielo/.local/lib/python3.5/site-packages/pymongo /collection.py", line 2397, in aggregate
**kwargs)
File "/home/danielo/.local/lib/python3.5/site-packages/pymongo/collection.py", line 2242, in _aggregate
common.validate_list('pipeline', pipeline)
File "/home/danielo/.local/lib/python3.5/site-packages/pymongo/common.py", line 428, in validate_list
raise TypeError("%s must be a list" % (option,))
TypeError: pipeline must be a list
UPDATE 2
This code runs without problems, but it make nothing of his purpose, the collection pub_fulltext have anything, when it should have data.
import pymongo
client=pymongo.MongoClient("localhost",27017)
db=client.publications
collec=db.zikaVirus2
pipeline=db.collec.aggregate([
{"$match":{"fullText":{"$exists": "true"}}},
{"$out": "pub_fulltext"}
])
for item in pipeline:
db.pub_fulltext.aggregate(item)
Then I try this:
import pymongo
client=pymongo.MongoClient("localhost",27017)
db=client.publications
collec=db.zikaVirus2
pipeline=[db.collec.aggregate([
{"$match":{"fullText":{"$exists": "true"}}},
{"$out": "pub_fulltext"}
])]
for item in db.collection.aggregate(pipeline):
db.collection.aggregate(item)
Getting this error:
Traceback (most recent call last):
File "genColFulltext.py", line 10, in <module>
for item in collection.aggregate(pipeline):
Traceback (most recent call last): File "genColFulltext.py", line 10, in <module>
for item in db.collection.aggregate(pipeline): File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pymongo/collection.py", line 2397, in aggregate
**kwargs) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pymongo/collection.py", line 2304, in _aggregate
client=self.__database.client) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pymongo/pool.py", line 584, in command
self._raise_connection_failure(error) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pymongo/pool.py", line 745, in _raise_connection_failure
raise error File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pymongo/pool.py", line 579, in command
unacknowledged=unacknowledged) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pymongo/network.py", line 114, in command
codec_options, ctx=compression_ctx) File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pymongo/message.py", line 679, in _op_msg
flags, command, identifier, docs, check_keys, opts) bson.errors.InvalidDocument: Cannot encode object: <pymongo.command_cursor.CommandCursor object at 0x1008e4198>