How to make a query with several pipes with python on a MongoDB database [Errno 111]?

I want to make a query about a mongoDB database with a python script that will allow me to modify the query about the schedule. However I am not able to visualize the result:

#!/usr/bin/python

import pymongo
import datetime
import pprint

from pymongo import MongoClient

client = MongoClient('mongodb://swiper_read:...')

db = MongoClient().aggregation_example

# // Pipeline
pipeline =[
         { "subscribedFlux": { "$exists": "true" } }
    ]

a = pprint.pprint(list(db.things.aggregate(pipeline)))

print a

But the terminal tells me:

:~$ python testMongoDB.py 
/home/antoine/anaconda2/lib/python2.7/site-packages/pymongo/common.py:555: UserWarning: Unknown option 3t.databases
  warnings.warn(str(exc))
/home/antoine/anaconda2/lib/python2.7/site-packages/pymongo/common.py:555: UserWarning: Unknown option 3t.uriVersion
  warnings.warn(str(exc))
/home/antoine/anaconda2/lib/python2.7/site-packages/pymongo/common.py:555: UserWarning: Unknown option 3t.connectionMode
  warnings.warn(str(exc))
/home/antoine/anaconda2/lib/python2.7/site-packages/pymongo/common.py:555: UserWarning: Unknown option 3t.connection.name
  warnings.warn(str(exc))
Traceback (most recent call last):
  File "testMongoDB.py", line 47, in <module>
    a = pprint.pprint(list(db.multifeeds.aggregate(pipeline))) # fue lo que utilisaba antes
  File "/home/antoine/anaconda2/lib/python2.7/site-packages/pymongo/collection.py", line 1845, in aggregate
    with self._socket_for_reads() as (sock_info, slave_ok):
  File "/home/antoine/anaconda2/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "/home/antoine/anaconda2/lib/python2.7/site-packages/pymongo/mongo_client.py", line 859, in _socket_for_reads
    with self._get_socket(read_preference) as sock_info:
  File "/home/antoine/anaconda2/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "/home/antoine/anaconda2/lib/python2.7/site-packages/pymongo/mongo_client.py", line 823, in _get_socket
    server = self._get_topology().select_server(selector)
  File "/home/antoine/anaconda2/lib/python2.7/site-packages/pymongo/topology.py", line 214, in select_server
    address))
  File "/home/antoine/anaconda2/lib/python2.7/site-packages/pymongo/topology.py", line 189, in select_servers
    self._error_message(selector))
pymongo.errors.ServerSelectionTimeoutError: localhost:27017: [Errno 111] Connection refused

There is an information about where this pymongo is:

$ pip install pymongo
Requirement already satisfied: pymongo in ./anaconda2/lib/python2.7/site-packages

I do not have mongod.conf mongodb.conf in etc

Update 24/5/2017

I installed mongodb-server:

sudo apt install mongodb-server

And today I have an error

exception: Unrecognized pipeline stage name: '$count'

I think, according to ares, which gives an answer about SO in English I do not have the latest version of mongodb but it also allows me to do:

pipeline =[
        {
            "$match": {
             "subscribedFlux": { "$exists": "true" }
            }
        },


       {
        "$group": {
          "_id" : "null", 
          "count" : {"$sum" : "1"}
        }
      }
    ]

and get a result that is not true according to:

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