cx_Oracle doesn't connect when using SID instead of service name on connection string

I a similar scenario, I was able to connect to the database by using cx_Oracle.makedsn() to create a dsn string with a given SID (instead of the service name):

dsnStr = cx_Oracle.makedsn("oracle.sub.example.com", "1521", "ora1")

This returns something like

(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle.sub.example.com)(PORT=1521)))(CONNECT_DATA=(SID=ora1)))

which can then be used with cx_Oracle.connect() to connect to the database:

con = cx_Oracle.connect(user="myuser", password="mypass", dsn=dsnStr)print con.versioncon.close()

For those looking for how to specify service_name instead of SID.

From changelog for SQLAlchemy 1.0.0b1 (released on March 13, 2015):

[oracle] [feature] Added support for cx_oracle connections to a specific service name, as opposed to a tns name, by passing ?service_name=<name> to the URL. Pull request courtesy Sławomir Ehlert.

The change introduces new, Oracle dialect specific option service_name which can be used to build connect string like this:

from sqlalchemy import create_enginefrom sqlalchemy.engine import urlconnect_url = url.URL(    'oracle+cx_oracle',    username='some_username',    password='some_password',    host='some_host',    port='some_port',    query=dict(service_name='some_oracle_service_name'))engine = create_engine(connect_url)

If you are using sqlalchemy and ORACLE 12, the following seems to work.

from sqlalchemy import create_enginecon='oracle://user:password@hostname:1521/?service_name=DDDD'engine = create_engine(con)

Note, you have to use the service name and not the SID. I don't know why, but the simple connection string that uses SID does not work.