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how to get the latest database collection from MongoDB with Mongo Engine

I am very new to MongoDB. I create a database within a loop. Each time (Every 2 hours), I get data from some sources and create a data collection by MongoEngine and name each collection based on the creation time (for example 05_01_2021_17_00_30).
Now, on another python code , I want to get the latest database. how can I call the latest database collection without knowing the name of it?
I saw some guidelines in Stackoverflow but codes are old and not working now. Thanks guys.

I came up with this answer:
In mongo_setup.py: when I want to create a database, it will be named after the time of creation and save the name in a text file.
import mongoengine
import datetime
def global_init():
nownow = datetime.datetime.now()
Update_file_name = str(nownow.strftime("%d_%m_%Y_%H_%M_%S"))
# For Shaking hand between Django and the last updated data base, export the name
of the latest database
# in a text file and from there, Django will understand which database is the
latest
Updated_txt = open('.\\Latest database to read for Django.txt', '+w')
Updated_txt.write(Update_file_name)
Updated_txt.close()
mongoengine.register_connection(alias='core', name=Update_file_name)
In Django views.py: we will call the text file and read the latest database's name:
database_name_text_file = 'directory of the text file...'
db_name_file = open(database_name_text_file, 'r')
db_name = db_name_file.read()
# MongoDb Database
myclient = MongoClient(port=27017)
mydatabase = myclient[db_name]
classagg = mydatabase['aggregation__class']
database_text = classagg.find()
for i in database_text:
....

SQLAlchemy Postgres query is key exists in JSON

I have a model Definition:
class Definition:
meta = Column(MutableDict.as_mutable(JSON))
It stores any JSON so I want to query if a given key exists in this field.
I need something like:
defs = db.query(Definition).filter(
Definition.meta.has_key('translation')).all()
MySQL for example has a function named json_contains and I could use it:
defs = db.query(Definition).filter(
func.json_contains(
Definition.meta, 'translation') == 1).all()
How can I achieve this in PostgreSQL

Whenever I am unsure of how to use the sqlalchemy bits, I hack a version together, and go from there:
json_select = '''SELECT jdoc->'key_name1', jdoc->'translation'
FROM Definition
WHERE jdoc #> '{"translation": 1, "key_name1": "hello there"}'
;
'''
print([x for x in db.engine.execute(json_select)])
note:
psycopg2 changed in version 2.5.4: added jsonb support.
Referenced:
http://initd.org/psycopg/docs/extras.html#json-adaptation
https://www.postgresql.org/docs/9.4/static/datatype-json.html

Get all documents of a collection using Pymongo

I want to write a function to return all the documents contained in mycollection in mongodb
from pymongo import MongoClient
if __name__ == '__main__':
client = MongoClient("localhost", 27017, maxPoolSize=50)
db=client.mydatabase
collection=db['mycollection']
cursor = collection.find({})
for document in cursor:
print(document)
However, the function returns: Process finished with exit code 0

Here is the sample code which works fine when you run from command prompt.
from pymongo import MongoClient
if __name__ == '__main__':
client = MongoClient("localhost", 27017, maxPoolSize=50)
db = client.localhost
collection = db['chain']
cursor = collection.find({})
for document in cursor:
print(document)
Please check the collection name.

pymongo creates a cursor. Hence you'll get the object 'under' the cursor. To get all objects in general try:
list(db.collection.find({}))
This will force the cursor to iterate over each object and put it in a list()
Have fun...

I think this will work fine in your program.
cursor = db.mycollection # choosing the collection you need
for document in cursor.find():
print (document)

it works fine for me,try checking the exact database name and collection name.
and try changing from db=client.mydatabase to db=client['mydatabase'] .
If your database name is such that using attribute style access won’t work (like test-database), you can use dictionary style access instead.
source !

List names of all available MS SQL databases on server using python

Trying to list the names of the databases on a remote MS SQL server using Python (Just like the Object Explorer in MS SQL Server Management Studio).
Current solution: The required query is SELECT name FROM sys.databases;. So current solution is using SQLAlchemy and Pandas, which works fine as below.
import pandas
from sqlalchemy import create_engine
#database='master'
engine = create_engine('mssql+pymssql://user:password#server:port/master')
query = "select name FROM sys.databases;"
data = pandas.read_sql(query, engine)
output:
name
0 master
1 tempdb
2 model
3 msdb
Question: How to list the names of the databases on the server using
SQLAlchemy's inspect(engine) similar to listing table names under a database? Or any simpler way without importing Pandas?
from sqlalchemy import inspect
#trial 1: with no database name
engine = create_engine('mssql+pymssql://user:password#server:port')
#this engine not have DB name
inspector = inspect(engine)
inspector.get_table_names() #returns []
inspector.get_schema_names() #returns [u'dbo', u'guest',...,u'INFORMATION_SCHEMA']
#trial 2: with database name 'master', same result
engine = create_engine('mssql+pymssql://user:password#server:port/master')
inspector = inspect(engine)
inspector.get_table_names() #returns []
inspector.get_schema_names() #returns [u'dbo', u'guest',...,u'INFORMATION_SCHEMA']

If all you really want to do is avoid importing pandas then the following works fine for me:
from sqlalchemy import create_engine
engine = create_engine('mssql+pymssql://sa:saPassword#localhost:52865/myDb')
conn = engine.connect()
rows = conn.execute("select name FROM sys.databases;")
for row in rows:
print(row["name"])
producing
master
tempdb
model
msdb
myDb

It is also possible to obtain tables from a specific scheme with execute the single query with the driver below: DB-API interface to Microsoft SQL Server for Python.
pip install pymssql
import pymssql
# Connect to the database
conn =
pymssql.connect(server='127.0.0.1',user='root',password='root',database='my_database')
# Create a Cursor object
cur = conn.cursor()
# Execute the query: To get the name of the tables from my_database
cur.execute("select table_name from information_schema.tables") # where table_schema = 'tableowner'
for row in cur.fetchall():
# Read and print tables
for row in cur.fetchall():
print(row[0])
output:
my_table_name_1
my_table_name_2
my_table_name_3
...
my_table_name_x

I believe the following snippet will list the names of the available databases on whatever server you choose to connect to. This will return a JSON object that will be displayed in your browser. This question is a bit old, but I hope this helps anyone curious who stops by.
from flask import Flask, request
from flask_restful import Resource, Api
from sqlalchemy import create_engine, inspect
from flask_jsonpify import jsonify
engine = create_engine('mssql+pymssql://user:password#server:port/master')
class AllTables(Resource):
def get(self):
conn = engine.connect()
inspector = inspect(conn)
tableList = [item for item in inspector.get_table_names()]
result = {'data': tableList}
return jsonify(result)
api.add_resource(AllTables, '/alltables')
app.run(port='8080')

here is another solution which fetch row by row:
import pymssql
connect = pymssql.connect(server, user, password, database)
cursor = connect.cursor(as_dict=True)
row = cursor.fetchone()
while row:
for r in row.items():
print r[0], r[1]
row = cursor.fetchone()

How to delete a MongoDB collection in PyMongo

How to check in PyMongo if collection exists and if exists empty (remove all from collection)?
I have tried like
collection.remove()
or
collection.remove({})
but it doesn't delete collection. How to do that ?

Sample code in Pymongo with comment as explanation:
from pymongo import MongoClient
connection = MongoClient('localhost', 27017) #Connect to mongodb
print(connection.database_names()) #Return a list of db, equal to: > show dbs
db = connection['testdb1'] #equal to: > use testdb1
print(db.list_collection_names()) #Return a list of collections in 'testdb1'
print("posts" in db.list_collection_names()) #Check if collection "posts"
# exists in db (testdb1)
collection = db['posts']
print(collection.count() == 0) #Check if collection named 'posts' is empty
collection.drop() #Delete(drop) collection named 'posts' from db and all documents contained.

You should use .drop() instead of .remove(), see documentation for detail: http://api.mongodb.org/python/current/api/pymongo/collection.html#pymongo.collection.Collection.drop
=====
Sorry for misunderstanding your question.
To check if a collection exists, use method collection_names on database:
>>> collection_name in database.list_collection_names()
To check if a collection is empty, use:
>>> collection.count() == 0
both will return True or False in result.

Have you tried this:
db.collection.remove();