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cannot access mysql database through python flask

I am attempting to create a flask web application that uses mysql to store users and some other data. When I use the following code
import MySQLdb
def connection():
conn = MySQLdb.connect(host='localhost', user='root', passwd='password', database='data')
c = conn.cursor()
return c, conn
I get a 500 internal service error. This code will connect on the command line, and my flask site works fine until I add the line
from dbconnect import connection
I have tried using different ways to connect to the database, (python connector, pymysql). They all give the same error. I have also tried updating permissions from inside mysql to the user. I have been following tutorials from https://pythonprogramming.net/flask-connect-mysql-using-mysqldb-tutorial/ but they did not get these errors in the tutorial and I have followed most of the tutorial exactly.

Connecting psycopg2 with Python in Heroku

I've been trying for some days to connect my python 3 script to PostgresSQL database(psycopg2) in Heroku, without Django.
I found some article and related questions, but I had to invest a lot of time to get something that I thought should be very straightforward, even for a newbie like me.
I eventually made it work somehow but hopefully posting the question (and answer) will help other people to achieve it faster.
Of course, if anybody has a better way, please share it.
As I said, I had a python script that I wanted to make it run from the cloud using Heroku. No Django involved (just a script/scraper).
Articles that I found helpful at the beginning, even if they were not enough:
Running Python Background Jobs with Heroku
Simple twitter-bot with Python, Tweepy and Heroku

Main steps:
1. Procfile
Procfile has to be:
worker: python3 folder/subfolder/myscript.py
2. Heroku add-on
Add-on Heroku Postgres :: Database has to be added to the appropriate personal app in the heroku account.
To make sure this was properly set, this was quite helpful.
3. Python script with db connection
Finally, to create the connection in my python script myscript.py, I took this article as a reference and adapted it to Python 3:
import psycopg2
import urllib.parse as urlparse
import os
url = urlparse.urlparse(os.environ['DATABASE_URL'])
dbname = url.path[1:]
user = url.username
password = url.password
host = url.hostname
port = url.port
con = psycopg2.connect(
dbname=dbname,
user=user,
password=password,
host=host,
port=port
)
To create a new database, this SO question explains it. Key line is:
con.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT)

You can do it using the SQLALCHEMY library.
First, you need to install the SQLALCHEMY library using pip, if you don't have pip on your computer install, you will know-how using a simple google search
pip install sqlalchemy
Here is the code snippet that do what you want:
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker
import os
# Put your URL in an environment variable and connect.
engine = create_engine(os.getenv("DATABASE_URL"))
db = scoped_session(sessionmaker(bind=engine))
# Some variables you need.
var1 = 12
var2 = "Einstein"
# Execute statements
db.execute("SELECT id, username FROM users WHERE id=:id, username=:username"\
,{"id": var1, "username": var2}).fetchall()
# Don't forget to commit if you did an insertion,etc...
db.commit()

I wasn't able to parse the DATABASE_URL provided by Heroku with the urllib.parse as suggested above, but the following worked for me:
The URL I retrieved from Heroku was in the format:
postgres://username:password#host:port/database
for example:
postgres://jticiuimwernbk:ff78903549d4c6ec13a53a8ffefcd201b937d54c35d976
#ec2-52-123-182-987.compute-1.amazonaws.com:5432/dbsd4fdf6c1awq
So I manually dissected it as follows:
user = 'jticiuimwernbk'
password = 'ff78903549d4c6ec13a53a8ffefcd201b937d54c35d976'
host = 'ec2-52-123-182-987.compute-1.amazonaws.com'
port = '5432'
database = 'dbsd4fdf6c1awq'
#Then created the connection using the above:
con = psycopg2.connect(database=database,
user=user,
password=password,
host=host,
port=port)
# and now I was able to perform queries:
cur = conn.cursor()
results = cur.execute("<some SQL query>;").fetchall()
cur.close()
conn.close()

Trouble connecting to SQL server with python

I have recently installed Microsoft SQL Server 2014 on my PC as I want to create a database for a web application I am building (I have been learning Python for a year and have very basic experience with SQLite).
After installing SQL Server 2014 and creating a database called Users, I am just trying to run some very basic commands to my database but I am falling at the first hurdle over and over!
I have installed pymssql and pyodbc and tried running commands directly with these but have failed. (e.g. pymssql gives me a TypeError: argument of type 'NoneType' is not iterable when I set the variable conn = pymssql.connect(server, user, password, "tempdb")
My latest attempt is to use SQLalchemy to achieve my long awaited connection with SQL database. However, after installing this, it is failing on the following error:
"sqlalchemy.exc.OperationalError: (pymssql.OperationalError) (20009, 'DB-Lib error message 20009, severity 9:\nUnable to connect: Adaptive Server is unavailable or does not exist\nNet-Lib error during Unknown error (10035)\n')"
The question I need answering is, how do I start talking to my database using SQLalchemy?
The code I am using is as follows:
from sqlalchemy import *
engine = create_engine('mssql+pymssql://Han & Lew:#SlugarPlum:1433/Users')
m = MetaData()
t = Table('t', m,
Column('id', Integer, primary_key=True),
Column('x', Integer))
m.create_all(engine)
Yes, my PC is called SlugarPlum. User is Han & Lew. And my server is called THELROYSERVER. DSN = 1433. No password. (I don't know if it is wise that I am giving this information online but the data I have is not sensitive so I guess it's worth a shot.)
Also, if anyone can direct me to an ultra-beginners resource for Python-SQL server that would be awesome as I am getting beaten up by how complex this seems to be!

Here's a connect function and example for connecting via pyodbc. Connecting via pymssql should be as easy as formatting the connecting string for pymssql. I've provided Windows and Linux options, but only tested on Linux. I hope it helps.
def sqlalchemy_connect(connect_string):
""" Connect to the database via ODBC, start SQL Alchemy engine. """
def connect():
return pyodbc.connect(connect_string, autocommit=True)
db = create_engine('mssql://', creator=connect)
db.echo = False
return db
def main():
global DBCONN
# Linux with FreeTDS
connect_string = "DRIVER={FreeTDS};SERVER=<server name>;PORT=<port num>;DATABASE=<db>;UID=<user>;PWD=<password>;TDS_Version=<version num>;"
# Windows with SQL Server
connect_string = "DRIVER={SQL Server};SERVER=<server name>;PORT=<port num>;DATABASE=<db>;UID=<user>;PWD=<password>;"
DBCONN = sqlalchemy_connect(connect_string)
if __name__ == "__main__":
main()

Adaptive Server connection failed error in Python/Flask/sqlAlchemy environment with pymssql

Update: I've confirmed this is only a problem when using an Azure SQL instance. I can use the same conn string to connect to local, network, and remote SQL (AWS) instances - it is only failing when connecting to Azure. I can connect to the Azure instance with other tools, like Management Studio.
I am building a small Python(3.4.x)/Flask application. I'm a complete noob here so forgive me if I break any rules in posting.
I have created the database engine with:
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker
from sqlalchemy.ext.declarative import declarative_base
engine = create_engine('mssql+pymssql://dbadmin:dbadminpass#somedomain.server.net/databasename?charset=utf8')
db_session = scoped_session(sessionmaker(autocommit = False, autoflush = False, bind = engine))
Base = declarative_base()
Base.query = db_session.query_property()
def init_db():
import models
Base.metadata.creat_all(bind=engine)
Everything builds/interprets correctly at runtime but I get an error on running the query:
usr = User.query.filter_by(username=form.user.data).first()
The error is:
sqlalchemy.exc.OperationalError: (OperationalError) (20002, b'DB-Lib error message 20002, severity 9:\nAdaptive Server connection failed\n') None None
packages are: Flask==0.10.1, pymssql==2.1.1, SQLAlchemy==0.9.8
Thanks in advance.

I had similar problem and solved it by explicitly setting tds version = 7.0. FreeTDS reads the user's ${HOME}/.freetds.conf before resorting to the system-wide sysconfdir/freetds.conf. So, I created ~/.freetds.conf with [global] section as:
[global]
tds version = 7.0
You can find more information on freetds.con: http://www.freetds.org/userguide/freetdsconf.htm

As I just had the same problem.
Since I could get pymssql to connect bypassing sqlalchemy, I figured everything else should be fine, so I used the create_engine parameter connect_args to pass everything straight to pymssql.connect.
server_name = "sql_server_name"
server_addres = server_name + ".database.windows.net"
database = "database_name"
username = "{}#{}".format("my_username", server_name)
password = "strong_password"
arguments = dict(server=server_addres, user=username,
password=password, database=database, charset="utf8")
AZURE_ENGINE = create_engine('mssql+pymssql:///', connect_args=arguments)
This works fine and does not require one to meddle with the .freetds.conf file at all.
Also, note that pymssql requires usernname to be in the form username#servername. For more information see the linked documentation.

Connecting to SQL Server 2012 using sqlalchemy and pyodbc

I'm trying to connect to a SQL Server 2012 database using SQLAlchemy (with pyodbc) on Python 3.3 (Windows 7-64-bit). I am able to connect using straight pyodbc but have been unsuccessful at connecting using SQLAlchemy. I have dsn file setup for the database access.
I successfully connect using straight pyodbc like this:
con = pyodbc.connect('FILEDSN=c:\\users\\me\\mydbserver.dsn')
For sqlalchemy I have tried:
import sqlalchemy as sa
engine = sa.create_engine('mssql+pyodbc://c/users/me/mydbserver.dsn/mydbname')
The create_engine method doesn't actually set up the connection and succeeds, but
iIf I try something that causes sqlalchemy to actually setup the connection (like engine.table_names()), it takes a while but then returns this error:
DBAPIError: (Error) ('08001', '[08001] [Microsoft][ODBC SQL Server Driver][DBNETLIB]SQL Server does not exist or access denied. (17) (SQLDriverConnect)') None None
I'm not sure where thing are going wrong are how to see what connection string is actually being passed to pyodbc by sqlalchemy. I have successfully using the same sqlalchemy classes with SQLite and MySQL.

The file-based DSN string is being interpreted by SQLAlchemy as server name = c, database name = users.
I prefer connecting without using DSNs, it's one less configuration task to deal with during code migrations.
This syntax works using Windows Authentication:
engine = sa.create_engine('mssql+pyodbc://server/database')
Or with SQL Authentication:
engine = sa.create_engine('mssql+pyodbc://user:password#server/database')
SQLAlchemy has a thorough explanation of the different connection string options here.

In Python 3 you can use function quote_plus from module urllib.parse to create parameters for connection:
import urllib
params = urllib.parse.quote_plus("DRIVER={SQL Server Native Client 11.0};"
"SERVER=dagger;"
"DATABASE=test;"
"UID=user;"
"PWD=password")
engine = sa.create_engine("mssql+pyodbc:///?odbc_connect={}".format(params))
In order to use Windows Authentication, you want to use Trusted_Connection as parameter:
params = urllib.parse.quote_plus("DRIVER={SQL Server Native Client 11.0};"
"SERVER=dagger;"
"DATABASE=test;"
"Trusted_Connection=yes")
In Python 2 you should use function quote_plus from library urllib instead:
params = urllib.quote_plus("DRIVER={SQL Server Native Client 11.0};"
"SERVER=dagger;"
"DATABASE=test;"
"UID=user;"
"PWD=password")

I have an update info about the connection to MSSQL Server without using DSNs and using Windows Authentication. In my example I have next options:
My local server name is "(localdb)\ProjectsV12". Local server name I see from database properties (I am using Windows 10 / Visual Studio 2015).
My db name is "MainTest1"
engine = create_engine('mssql+pyodbc://(localdb)\ProjectsV12/MainTest1?driver=SQL+Server+Native+Client+11.0', echo=True)
It is needed to specify driver in connection.
You may find your client version in:
control panel>Systems and Security>Administrative Tools.>ODBC Data
Sources>System DSN tab>Add
Look on SQL Native client version from the list.

Just want to add some latest information here:
If you are connecting using DSN connections:
engine = create_engine("mssql+pyodbc://USERNAME:PASSWORD#SOME_DSN")
If you are connecting using Hostname connections:
engine = create_engine("mssql+pyodbc://USERNAME:PASSWORD#HOST_IP:PORT/DATABASENAME?driver=SQL+Server+Native+Client+11.0")
For more details, please refer to the "Official Document"

import pyodbc
import sqlalchemy as sa
engine = sa.create_engine('mssql+pyodbc://ServerName/DatabaseName?driver=SQL+Server+Native+Client+11.0',echo = True)
This works with Windows Authentication.

I did different and worked like a charm.
First you import the library:
import pandas as pd
from sqlalchemy import create_engine
import pyodbc
Create a function to create the engine
def mssql_engine(user = os.getenv('user'), password = os.getenv('password')
,host = os.getenv('SERVER_ADDRESS'),db = os.getenv('DATABASE')):
engine = create_engine(f'mssql+pyodbc://{user}:{password}#{host}/{db}?driver=SQL+Server')
return engine
Create a variable with your query
query = 'SELECT * FROM [Orders]'
Execute the Pandas command to create a Dataframe from a MSSQL Table
df = pd.read_sql(query, mssql_engine())