用Python訪問Oracle

Despite the beaming praise for the simplicity of the cx_Oracle project on their SourceForge page, I had trouble using the Python module to create a connection to an Oracle database. It turns out that the module is quite nice once you get past a couple of problems that have nothing to do with the cx_Oracle module. In my case, my computer’s environment and some confusing information on the Internet were the cause of my troubles. So here I have organized some hints to help you if you are unfortunate and cannot immediately make a successful connection to your Oracle database using cx_Oracle.

Install the Correct Version of cx_Oracle

This was my biggest problem, though I didn’t realize it for a while. The cx_Oracle project has separate binary distributions for both OS and Oracle version, which support Windows and CentOS for Oracle 10.2, 11.1 and 11.2. On Windows for sure, installing the wrong binary will result in a broken installation. However, it’s not necessarily as simple as knowing which version your Oracle database is at.

Here’s what happened in my case. I have an Oracle ODBC driver installed on my Windows XP installation (OraClient10g) but I want to connect to an 11g database. I first assumed that I needed to install the 11g version of cx_Oracle and found that assumption to be wrong. I think because of the ODBC driver version, I had to install the 10g version of cx_Oracle. I simply could not connect to my database otherwise. I don’t have a way to confirm this ODBC complication because I don’t have authority to install different versions of drivers but it makes sense to me.

The indication I got that my connection was not working was the following error from my Python program:

CODE:

cx_Oracle.DatabaseError: ORA-24315: illegal attribute typeThis is a vague error that, I suppose, has something to do with the mismatch between the cx_Oracle code and the ODBC driver. Once I installed the cx_Oracle version that matched my ODBC driver version I was able to successfully connect.

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