On Apr 30, 2010, at 3:31 AM, dhanil anupurath wrote:
>
> import pkg_resources
> pkg_resources.require("cx-Oracle>=5.0.3")
> import cx_Oracle
>
> connstr='<username>/<password>@localhost'
> conn = cx_Oracle.connect(connstr)
I just want to go over how this is documented. From the cx_oracle
documentation at
http://cx-oracle.sourceforge.net/html/module.html#cx_Oracle.connect , we see
that the above is taken as the format "user/p...@dsn", where "dsn" is the TNS
name from your tnsnames.ora file - ideally it would be the string "xe", but it
seems to correlate the hostname of "localhost" as well.
Onto SQLAlchemy's, the document at
http://www.sqlalchemy.org/docs/reference/dialects/oracle.html?highlight=cx_oracle#connecting
states :
Connecting with create_engine() uses the standard URL approach of
oracle://user:p...@host:port/dbname[?key=value&key=value...]. If dbname is
present, the host, port, and dbname tokens are converted to a TNS name using
the cx_oracle makedsn() function. Otherwise, the host token is taken directly
as a TNS name.
So the equivalent connect string is:
create_engine('oracle://<user>:<password>@localhost')
meaning, '/dbname' is not present, so the 'host' portion, in this case
'localhost', is sent to cx_Oracle.connect as the TNS name.
The usual way to connect looks like:
create_engine('oracle://<user>:<password>@localhost/xe')
the advantage to this approach is that SQLAlchemy uses cx_Oracle.makedsn() so
that no TNS entry is required.
Here are all the ways to connect to a localhost XE server:
import cx_Oracle
print cx_Oracle.connect('scott/ti...@localhost')
print cx_Oracle.connect('scott/ti...@xe')
print cx_Oracle.connect('scott', 'tiger', 'localhost')
print cx_Oracle.connect('scott', 'tiger', 'xe')
print cx_Oracle.connect('scott', 'tiger', cx_Oracle.makedsn('localhost', 1521,
'xe'))
from sqlalchemy import create_engine
print
create_engine('oracle://scott:ti...@localhost').connect().connection.connection
print create_engine('oracle://scott:ti...@xe').connect().connection.connection
print
create_engine('oracle://scott:ti...@localhost/xe').connect().connection.connection
output of this looks like:
<cx_Oracle.Connection to sc...@localhost>
<cx_Oracle.Connection to sc...@xe>
<cx_Oracle.Connection to sc...@localhost>
<cx_Oracle.Connection to sc...@xe>
<cx_Oracle.Connection to
scott@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))(CONNECT_DATA=(SID=xe)))>
<cx_Oracle.Connection to sc...@localhost>
<cx_Oracle.Connection to sc...@xe>
<cx_Oracle.Connection to
scott@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))(CONNECT_DATA=(SID=xe)))>
note the two forms of connection that use makedsn() have a locally-generated
TNS entry present.
Also note that SQLAlchemy is not using pkg_resources to import cx_Oracle. It
just calls "import cx_Oracle". If the above pkg_resources call is required
(extremely unlikely), you need to call it before create_engine().
hope this helps.
> # tnsnames.ora Network Configuration File:
>
> XE =
> (DESCRIPTION =
> (ADDRESS = (PROTOCOL = TCP)(HOST =
> localhost.localdomain)(PORT = 1521))
> CONNECT_DATA = (SID = XE))
> )
>
> sqlnet.authentication_services = (NONE)
>
> LISTENER.ORA
> # listener.ora Network Configuration File:
>
> SID_LIST_LISTENER =
> (SID_LIST =
> (SID_DESC =
> (SID_NAME = PLSExtProc)
> (ORACLE_HOME = /usr/lib/oracle/xe/app/
> oracle/product/10.2.0/server)
> (PROGRAM = extproc)
> )
> (SID_DESC =
> (SID_NAME = m...@localhost)
> (ORACLE_HOME = /usr/lib/oracle/xe/app/oracle/
> product/10.2.0/server)
> )
> )
>
> LISTENER =
> (DESCRIPTION_LIST =
> (DESCRIPTION =
> (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
> (ADDRESS = (PROTOCOL = TCP)(HOST =
> localhost.localdomain)(PORT = 1521))
> )
> )
>
> DEFAULT_SERVICE_LISTENER = (XE)
>
> SQLNET.ORA
> This is the uncommented line in the sqlnet.ora
>
>
>
> 9.On googling ,I saw someone indicate that sql.authentication should
> be set to none.
> I did that but no avail.
>
> I would really appreciate any help in resolving this problem.
>
> Thanks.
>
>
>
>
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