cx_Oracle 5 Installation


Before cx_Oracle can be installed, an installation of Python is needed first. Python 2.7 and Python 3.4 and higher are supported.

You must also install an Oracle Client, if that has not been done already. Oracle Client versions 12.2, 12.1 and 11.2 are supported. The simplest Oracle Client is the free Oracle Instant Client. Only the “Basic” or “Basic Light” package is required at run-time. If you plan to build cx_Oracle from source, you will also need the “SDK” package. Oracle Client libraries and the SDK are also available in any Oracle Database installation or full Oracle Client installation.

Prebuilt binaries are available on PyPI for Windows and Linux. These can be downloaded and installed directly.

If no prebuilt binaries are available for your platform or you prefer to build from source you can download the source package from PyPI instead and run the following commands:

python build python install

You can also use pip, the generic tool for installing Python packages. It will download the source, compile and install the module for you. The command to use pip is the following:

python -m pip install cx_Oracle==5.3

If you run into any difficulty building from source, the BUILD.txt file can be consulted for hints on how to build. The Troubleshooting section below may also be of help. On Linux, if cx_Oracle needs to be compiled for the default python package, you will need the python-devel package or equivalent, which provides the Python.h header file.

Finally, you need an Oracle Database for Python to connect to. Oracle’s standard client-server version interoperability allows cx_Oracle to connect to both older and newer databases. Python can be local or remote to the database.

Oracle Database

Oracle Client libraries allow connection to older and newer databases. In summary, Oracle Client 12.2 can connect to Oracle Database 11.2 or greater. Oracle Client 12.1 can connect to Oracle Database 10.2 or greater. Oracle Client 11.2 can connect to Oracle Database 9.2 or greater. For additional information on which Oracle Database releases are supported by which Oracle client versions, please see Doc ID 207303.1.

Newer Oracle clients support new features, such as the oraaccess.xml external configuration file available with 12.1 or later clients, and session pool enhancements to dead connection detection in 12.2 clients.

The function clientversion() can be used to determine which Oracle Client version is in use and the attribute Connection.version can be used to determine which Oracle Database version a connection is accessing. These can then be used to adjust application behavior accordingly. Attempts to use some Oracle features that are not supported by a particular client/server combination may result in runtime errors. These include:

  • when attempting to access attributes that are not supported by the current Oracle Client library you will get the error “ORA-24315: illegal attribute type”
  • when attempting to use implicit results with Oracle Client 11.2 against Oracle Database 12c you will get the error “ORA-29481: Implicit results cannot be returned to client”
  • when attempting to get array DML row counts with Oracle Client 11.2 you will get the error “DPI-1013: not supported”


If installation fails:

  • Use option -v with pip. Review your output and logs. Try to install using a different method. Google anything that looks like an error. Try some potential solutions.
  • Was there a network connection error? Do you need to see the environment variables http_proxy and/or https_proxy?
  • Do you get the error “No module named pip”? The pip module is builtin to Python from version 2.7.9 but is sometimes removed by the OS. Use the venv module (builtin to Python 3.x) or virtualenv module (Python 2.x) instead.

If importing cx_Oracle fails:

  • Check the PATH environment variable on Windows. Ensure that you have restarted your command prompt if you have modified environment variables.
  • Check the LD_LIBRARY_PATH environment variable on Linux.
  • On macOS, make sure Oracle Instant Client is in ~/lib or /usr/local/lib and that you are not using the bundled Python (use Homebrew or instead).
  • Check that Python, cx_Oracle and your Oracle Client libraries are all 64-bit or all 32-bit.
  • on Windows, check that the correct Windows redistributables have been installed.
  • If you have both Python 2 and 3 installed, make sure you are using the correct python and pip (or python3 and pip3) executables.