Building a connection URL for mssql+pyodbc with sqlalchemy.engine.url.URL

Question

The problem...

I am trying to connect to a MSSql server via SQLAlchemy. Here is my code with fake credentials (not my real credentials obviously).

The code...

credentials = {
'username'  : 'SPOTTER_xyz_ACC',
'password'  : '123Goodbye2016!@#',
'host'      : 'MARYLQLT01',
'database'  : 'LRS_DUS',
'port'      : '1560'}

connect_url = sqlalchemy.engine.url.URL(
    'mssql+pyodbc',
    username=credentials['username'],
    password=credentials['password'],
    host=credentials['host'],
    port=credentials['port'],
    query=dict(service_name=credentials['database']))

engine = create_engine(connect_url)
connection=engine.connect()

And this is the .pyodbc error that I am getting.

(pyodbc.Error) ('IM002', '[IM002] [Microsoft][ODBC Driver Manager] Data source
name not found and no default driver specified (0) (SQLDriverConnect)')

Additional Details

But, here is what is weird... I if make a pyodbc connection and use Pandas.read_sql, then I can get data without an error. So I do not understand why I am getting a 'pyodbc' error????

connection=pyodbc.connect(\
                          'Driver={SQL Server}; \
                          Server=MARYLQLT01; \
                          Database=LRS_DUS; \
                          UID=SPOTTER_xyz_ACC; \
                          PWD=123Goodbye2016!@#')

stmt='select * from PD_SC_All'
df=pd.read_sql(stmt,connection)

And then I can see the dataframe.

So, why am I getting the (pyodbc.Error) when I try to connect with SQLAlchemy?

System Information

Windows 7
SQLAlchemy: 1.1.11
pyodbc: 4.0.16

Python 3.6.1 |Anaconda custom (64-bit)| (default, May 11 2017, 13:25:24) [MSC v.1900 64 bit (AMD64)]
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Answer 1

As stated in the SQLAlchemy documentation, for mssql+pyodbc connections

Hostname-based connections are not preferred, however are supported. The ODBC driver name must be explicitly specified:

engine = create_engine("mssql+pyodbc://scott:tiger@myhost:port/databasename?driver=SQL+Server+Native+Client+10.0")

For

credentials = {
    'username': 'scott',
    'password': 'tiger',
    'host': 'myhost',
    'database': 'databasename',
    'port': '1560'}

your statement

connect_url = sqlalchemy.engine.url.URL(
    'mssql+pyodbc',
    username=credentials['username'],
    password=credentials['password'],
    host=credentials['host'],
    port=credentials['port'],
    query=dict(service_name=credentials['database']))

produces the connect_url

mssql+pyodbc://scott:tiger@myhost:1560?service_name=databasename

What you really need is

connect_url = sqlalchemy.engine.url.URL(
    'mssql+pyodbc',
    username=credentials['username'],
    password=credentials['password'],
    host=credentials['host'],
    port=credentials['port'],
    database=credentials['database'],
    query=dict(driver='SQL+Server'))

which produces

mssql+pyodbc://scott:tiger@myhost:1560/databasename?driver=SQL+Server