cx_Oracle 8 Installation

Overview

To use cx_Oracle 8 with Python and Oracle Database you need:

  • Python 3.5 and higher. Older versions of cx_Oracle may work with older versions of Python, for example see Installing cx_Oracle in Python 2
  • Oracle Client libraries. These can be from the free Oracle Instant Client, or those included in Oracle Database if Python is on the same machine as the database. Oracle client libraries versions 19, 18, 12, and 11.2 are supported on Linux, Windows and macOS. Users have also reported success with other platforms. Use the latest client possible: Oracle’s standard client-server version interoperability allows connection to both older and newer databases.
  • An Oracle Database, either local or remote.

The cx_Oracle module loads Oracle Client libraries which communicate over Oracle Net to an existing database. Oracle Net is not a separate product: it is how the Oracle Client and Oracle Database communicate.

../_images/cx_Oracle_arch.png

Fig. 2 cx_Oracle Architecture

Quick Start cx_Oracle Installation

  • Install Python 3, if not already available. On macOS you must always install your own Python.

    Python 3.5 and higher are supported by cx_Oracle 8. For Python 2, see Installing cx_Oracle in Python 2.

  • Install cx_Oracle from PyPI with:

    python -m pip install cx_Oracle --upgrade
    

    Note: if a binary wheel package is not available for your platform, the source package will be downloaded instead. This will be compiled and the resulting binary installed.

    The --user option may be useful, if you don’t have permission to write to system directories:

    python -m pip install cx_Oracle --upgrade --user
    

    If you are behind a proxy, add a proxy server to the command, for example add --proxy=http://proxy.example.com:80

  • Add Oracle 19, 18, 12 or 11.2 client libraries to your operating system library search path such as PATH on Windows or LD_LIBRARY_PATH on Linux. On macOS use init_oracle_client() in your application to pass the Oracle Client directory name, see Locating the Oracle Client Libraries. This is also usable on Windows.

    To get the libraries:

    • If your database is on a remote computer, then download and unzip the client libraries from the free Oracle Instant Client “Basic” or “Basic Light” package for your operating system architecture.

      Instant Client on Windows requires an appropriate Microsoft Windows Redistributables, see Installing cx_Oracle on Windows. On Linux, the libaio (sometimes called libaio1) package is needed. Oracle Linux 8 also needs the libnsl package.

    • Alternatively, use the client libraries already available in a locally installed database such as the free Oracle Database Express Edition (“XE”) release.

    Version 19, 18 and 12.2 client libraries can connect to Oracle Database 11.2 or greater. Version 12.1 client libraries can connect to Oracle Database 10.2 or greater. Version 11.2 client libraries can connect to Oracle Database 9.2 or greater.

  • Create a script like the one below:

    # myscript.py
    
    import cx_Oracle
    
    # Connect as user "hr" with password "welcome" to the "orclpdb1" service running on this computer.
    connection = cx_Oracle.connect("hr", "welcome", "localhost/orclpdb1")
    
    cursor = connection.cursor()
    cursor.execute("""
            SELECT first_name, last_name
            FROM employees
            WHERE department_id = :did AND employee_id > :eid""",
            did = 50,
            eid = 190)
    for fname, lname in cursor:
        print("Values:", fname, lname)
    

    Locate your Oracle Database username and password, and the database connection string. The connection string is commonly of the format hostname/servicename, using the hostname where the database is running, and using the service name of the Oracle Database instance.

    Substitute your username, password and connection string in the code. Run the Python script, for example:

    python myscript.py
    

You can learn how to use cx_Oracle from the API documentation and samples.

If you run into installation trouble, check out the section on Troubleshooting.

Oracle Client and Oracle Database Interoperability

cx_Oracle requires Oracle Client libraries. The libraries provide the necessary network connectivity to access an Oracle Database instance. They also provide basic and advanced connection management and data features to cx_Oracle.

The simplest way to get Oracle Client libraries is to install the free Oracle Instant Client “Basic” or “Basic Light” package. The libraries are also available in any Oracle Database installation or full Oracle Client installation.

Oracle’s standard client-server network interoperability allows connections between different versions of Oracle Client libraries and Oracle Database. For certified configurations see Oracle Support’s Doc ID 207303.1. In summary, Oracle Client 19, 18 and 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. The technical restrictions on creating connections may be more flexible. For example Oracle Client 12.2 can successfully connect to Oracle Database 10.2.

cx_Oracle uses the shared library loading mechanism available on each supported platform to load the Oracle Client libraries at runtime. It does not need to be rebuilt for different versions of the libraries. Since a single cx_Oracle binary can use different client versions and also access multiple database versions, it is important your application is tested in your intended release environments. Newer Oracle clients support new features, such as the oraaccess.xml external configuration file available with 12.1 or later clients, session pool improvements, improved high availability features, call timeouts, and other enhancements.

The cx_Oracle 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-1050: Oracle Client library must be at version 12.1 or higher”

Installing cx_Oracle on Linux

This section discusses the generic installation methods on Linux. To use Python and cx_Oracle RPM packages from yum on Oracle Linux, see Installing cx_Oracle RPMs on Oracle Linux.

Install cx_Oracle

The generic way to install cx_Oracle on Linux is to use Python’s Pip package to install cx_Oracle from PyPI:

python -m pip install cx_Oracle --upgrade

The --user option may be useful, if you don’t have permission to write to system directories:

python -m pip install cx_Oracle --upgrade --user

If you are behind a proxy, add a proxy server to the command, for example add --proxy=http://proxy.example.com:80

This will download and install a pre-compiled binary if one is available for your architecture. If a pre-compiled binary is not available, the source will be downloaded, compiled, and the resulting binary installed. Compiling cx_Oracle requires the Python.h header file. If you are using the default python package, this file is in the python-devel package or equivalent.

Install Oracle Client

Using cx_Oracle requires Oracle Client libraries to be installed. These provide the necessary network connectivity allowing cx_Oracle to access an Oracle Database instance.

  • If your database is on a remote computer, then download the free Oracle Instant Client “Basic” or “Basic Light” package for your operating system architecture. Use the RPM or ZIP packages, based on your preferences.
  • Alternatively, use the client libraries already available in a locally installed database such as the free Oracle Database Express Edition (“XE”) release.

Oracle Instant Client Zip Files

To use cx_Oracle with Oracle Instant Client zip files:

  1. Download an Oracle 19, 18, 12, or 11.2 “Basic” or “Basic Light” zip file: 64-bit or 32-bit, matching your Python architecture.

    The latest version is recommended. Oracle Instant Client 19 will connect to Oracle Database 11.2 or later.

  2. Unzip the package into a single directory that is accessible to your application. For example:

    mkdir -p /opt/oracle
    cd /opt/oracle
    unzip instantclient-basic-linux.x64-19.6.0.0.0dbru.zip
    
  3. Install the libaio package with sudo or as the root user. For example:

    sudo yum install libaio
    

    On some Linux distributions this package is called libaio1 instead.

    On recent Linux versions, such as Oracle Linux 8, you may also need to install the libnsl package.

  4. If there is no other Oracle software on the machine that will be impacted, permanently add Instant Client to the runtime link path. For example, with sudo or as the root user:

    sudo sh -c "echo /opt/oracle/instantclient_19_6 > /etc/ld.so.conf.d/oracle-instantclient.conf"
    sudo ldconfig
    

    Alternatively, set the environment variable LD_LIBRARY_PATH to the appropriate directory for the Instant Client version. For example:

    export LD_LIBRARY_PATH=/opt/oracle/instantclient_19_6:$LD_LIBRARY_PATH
    
  5. If you use optional Oracle configuration files such as tnsnames.ora, sqlnet.ora or oraaccess.xml with Instant Client, then put the files in an accessible directory, for example in /opt/oracle/your_config_dir. Then use:

    import cx_Oracle
    cx_Oracle.init_oracle_client(config_dir="/home/your_username/oracle/your_config_dir")
    

    Or set the environment variable TNS_ADMIN to that directory name.

    Alternatively, put the files in the network/admin subdirectory of Instant Client, for example in /opt/oracle/instantclient_19_6/network/admin. This is the default Oracle configuration directory for executables linked with this Instant Client.

Oracle Instant Client RPMs

To use cx_Oracle with Oracle Instant Client RPMs:

  1. Download an Oracle 19, 18, 12, or 11.2 “Basic” or “Basic Light” RPM: 64-bit or 32-bit, matching your Python architecture.

    Oracle’s yum server has Instant Client RPMs for Oracle Linux 7 and Instant Client RPMs for Oracle Linux 6 that can be downloaded without needing a click-through.

    The latest version is recommended. Oracle Instant Client 19 will connect to Oracle Database 11.2 or later.

  2. Install the downloaded RPM with sudo or as the root user. For example:

    sudo yum install oracle-instantclient19.6-basic-19.6.0.0.0-1.x86_64.rpm
    

    Yum will automatically install required dependencies, such as libaio.

    On recent Linux versions, such as Oracle Linux 8, you may need to manually install the libnsl package.

  3. For Instant Client 19, the system library search path is automatically configured during installation.

    For older versions, if there is no other Oracle software on the machine that will be impacted, permanently add Instant Client to the runtime link path. For example, with sudo or as the root user:

    sudo sh -c "echo /usr/lib/oracle/18.3/client64/lib > /etc/ld.so.conf.d/oracle-instantclient.conf"
    sudo ldconfig
    

    Alternatively, for version 18 and earlier, every shell running Python will need to have the environment variable LD_LIBRARY_PATH set to the appropriate directory for the Instant Client version. For example:

    export LD_LIBRARY_PATH=/usr/lib/oracle/18.3/client64/lib:$LD_LIBRARY_PATH
    
  4. If you use optional Oracle configuration files such as tnsnames.ora, sqlnet.ora or oraaccess.xml with Instant Client, then put the files in an accessible directory, for example in /opt/oracle/your_config_dir. Then use:

    import cx_Oracle
    cx_Oracle.init_oracle_client(config_dir="/opt/oracle/your_config_dir")
    

    Or set the environment variable TNS_ADMIN to that directory name.

    Alternatively, put the files in the network/admin subdirectory of Instant Client, for example in /usr/lib/oracle/19.6/client64/lib/network/admin. This is the default Oracle configuration directory for executables linked with this Instant Client.

Local Database or Full Oracle Client

cx_Oracle applications can use Oracle Client 19, 18, 12, or 11.2 libraries from a local Oracle Database or full Oracle Client installation.

The libraries must be either 32-bit or 64-bit, matching your Python architecture.

  1. Set required Oracle environment variables by running the Oracle environment script. For example:

    source /usr/local/bin/oraenv
    

    For Oracle Database Express Edition (“XE”) 11.2, run:

    source /u01/app/oracle/product/11.2.0/xe/bin/oracle_env.sh
    
  2. Optional Oracle configuration files such as tnsnames.ora, sqlnet.ora or oraaccess.xml can be placed in $ORACLE_HOME/network/admin.

    Alternatively, Oracle configuration files can be put in another, accessible directory. Then set the environment variable TNS_ADMIN to that directory name.

Installing cx_Oracle RPMs on Oracle Linux

Python and cx_Oracle RPM packages are available from the Oracle Linux yum server. Various versions of Python are easily installed. Using the yum server makes it easy to keep up to date.

Installation instructions are at Oracle Linux for Python Developers.

Installing cx_Oracle on Windows

Install cx_Oracle

Use Python’s Pip package to install cx_Oracle from PyPI:

python -m pip install cx_Oracle --upgrade

If you are behind a proxy, specify your proxy server:

python -m pip install cx_Oracle --proxy=http://proxy.example.com:80 --upgrade

This will download and install a pre-compiled binary if one is available for your architecture. If a pre-compiled binary is not available, the source will be downloaded, compiled, and the resulting binary installed.

Install Oracle Client

Using cx_Oracle requires Oracle Client libraries to be installed. These provide the necessary network connectivity allowing cx_Oracle to access an Oracle Database instance. Oracle Client versions 19, 18, 12 and 11.2 are supported.

  • If your database is on a remote computer, then download the free Oracle Instant Client “Basic” or “Basic Light” package for your operating system architecture.
  • Alternatively, use the client libraries already available in a locally installed database such as the free Oracle Database Express Edition (“XE”) release.

Oracle Instant Client Zip Files

To use cx_Oracle with Oracle Instant Client zip files:

  1. Download an Oracle 19, 18, 12, or 11.2 “Basic” or “Basic Light” zip file: 64-bit or 32-bit, matching your Python architecture.

    The latest version is recommended. Oracle Instant Client 19 will connect to Oracle Database 11.2 or later.

    Windows 7 users: Note that Oracle 19c is not supported on Windows 7.

  2. Unzip the package into a directory that is accessible to your application. For example unzip instantclient-basic-windows.x64-19.6.0.0.0dbru.zip to C:\oracle\instantclient_19_6.

  3. There are several alternative ways to tell cx_Oracle where your Oracle Client libraries are, see cx_Oracle 8 Initialization.

    • With Oracle Instant Client you can use init_oracle_client() in your application, for example:

      import cx_Oracle
      cx_Oracle.init_oracle_client(lib_dir=r"C:\oracle\instantclient_19_6")
      

      Note a ‘raw’ string is used because backslashes occur in the path.

    • Alternatively, add the Oracle Instant Client directory to the PATH environment variable. The directory must occur in PATH before any other Oracle directories. Restart any open command prompt windows.

    • Another way to set PATH is to use a batch file that sets it before Python is executed, for example:

      REM mypy.bat
      SET PATH=C:\oracle\instantclient_19_6;%PATH%
      python %*
      

      Invoke this batch file every time you want to run Python.

  4. Oracle Instant Client libraries require a Visual Studio redistributable with a 64-bit or 32-bit architecture to match Instant Client’s architecture. Each Instant Client version requires a different redistributable version:

  5. If you use optional Oracle configuration files such as tnsnames.ora, sqlnet.ora or oraaccess.xml with Instant Client, then put the files in an accessible directory, for example in C:\oracle\your_config_dir. Then use:

    import cx_Oracle
    cx_Oracle.init_oracle_client(config_dir=r"C:\oracle\your_config_dir")
    

    Or set the environment variable TNS_ADMIN to that directory name.

    Alternatively, put the files in a network\admin subdirectory of Instant Client, for example in C:\oracle\instantclient_19_6\network\admin. This is the default Oracle configuration directory for executables linked with this Instant Client.

Local Database or Full Oracle Client

cx_Oracle applications can use Oracle Client 19, 18, 12, or 11.2 libraries libraries from a local Oracle Database or full Oracle Client.

The Oracle libraries must be either 32-bit or 64-bit, matching your Python architecture.

  1. Set the environment variable PATH to include the path that contains OCI.DLL, if it is not already set.

    Restart any open command prompt windows.

  2. Optional Oracle configuration files such as tnsnames.ora, sqlnet.ora or oraaccess.xml can be placed in the network\admin subdirectory of the Oracle Database software installation.

    Alternatively, pass config_dir to init_oracle_client() as shown in the previous section, or set TNS_ADMIN to the directory name.

Installing cx_Oracle on macOS

Install Python

Make sure you are not using a bundled Python. These have restricted entitlements and will fail to load Oracle client libraries. Instead use Homebrew or Python.org.

Note Instant Client 19 and earlier are not supported on macOS 10.15 Catalina. You will need to allow access to several Instant Client libraries from the Security & Privacy preference pane.

Install cx_Oracle

Use Python’s Pip package to install cx_Oracle from PyPI:

python -m pip install cx_Oracle --upgrade

The --user option may be useful, if you don’t have permission to write to system directories:

python -m pip install cx_Oracle --upgrade --user

If you are behind a proxy, add a proxy server to the command, for example add --proxy=http://proxy.example.com:80

The source will be downloaded, compiled, and the resulting binary installed.

Install Oracle Instant Client

cx_Oracle requires Oracle Client libraries, which are found in Oracle Instant Client for macOS. These provide the necessary network connectivity allowing cx_Oracle to access an Oracle Database instance.

To use cx_Oracle with Oracle Instant Client zip files:

  1. Download the Oracle 19, 18, 12 or 11.2 “Basic” or “Basic Light” zip file from here. Choose either a 64-bit or 32-bit package, matching your Python architecture.

    The latest version is recommended. Oracle Instant Client 19 will connect to Oracle Database 11.2 or later.

  2. Unzip the package into a single directory that is accessible to your application. For example, in Terminal you could unzip in your home directory:

    cd ~
    unzip instantclient-basic-macos.x64-19.3.0.0.0dbru.zip
    

    This will create a directory /Users/your_username/instantclient_19_3.

  3. There are several alternative ways to tell cx_Oracle where your Oracle Instant Client libraries are, see cx_Oracle 8 Initialization.

    • You can use init_oracle_client() in your application:

      import cx_Oracle
      cx_Oracle.init_oracle_client(lib_dir="/Users/your_username/instantclient_19_3")
      
    • Alternatively, locate the directory with the cx_Oracle module binary and link or copy Oracle Instant Client to that directory. For example, if you installed cx_Oracle with --user in Python 3.8, then cx_Oracle.cpython-38-darwin.so might be in ~/Library/Python/3.8/lib/python/site-packages. You can then run ln -s ~/instantclient_19_3/libclntsh.dylib ~/Library/Python/3.8/lib/python/site-packages or copy the Instant Client libraries to that directory.

    • Alternatively, you can set DYLD_LIBRARY_PATH to the directory containing Oracle Instant Client, however this needs to be set in each terminal or process that invokes Python. The variable will not propagate to sub-shells.

    • Alternatively, on older versions of macOS, you could add a link to $HOME/lib or /usr/local/lib to enable applications to find Instant Client. If the lib sub-directory does not exist, you can create it. For example:

      mkdir ~/lib
      ln -s ~/instantclient_19_3/libclntsh.dylib ~/lib/
      

      Instead of linking, you can copy the required OCI libraries. For example:

      mkdir ~/lib
      cp ~/instantclient_19_3/{libclntsh.dylib.19.1,libclntshcore.dylib.19.1,libnnz19.dylib,libociei.dylib} ~/lib/
      

      For Instant Client 11.2, the OCI libraries must be copied. For example:

      mkdir ~/lib
      cp ~/instantclient_11_2/{libclntsh.dylib.11.1,libnnz11.dylib,libociei.dylib} ~/lib/
      
  4. If you use optional Oracle configuration files such as tnsnames.ora, sqlnet.ora or oraaccess.xml with Oracle Instant Client, then put the files in an accessible directory, for example in /Users/your_username/oracle/your_config_dir. Then use:

    import cx_Oracle
    cx_Oracle.init_oracle_client(config_dir="/Users/your_username/oracle/your_config_dir")
    

    Or set the environment variable TNS_ADMIN to that directory name.

    Alternatively, put the files in the network/admin subdirectory of Oracle Instant Client, for example in /Users/your_username/instantclient_19_3/network/admin. This is the default Oracle configuration directory for executables linked with this Instant Client.

Installing cx_Oracle without Internet Access

To install cx_Oracle on a computer that is not connected to the internet, download the appropriate cx_Oracle file from PyPI. Transfer this file to the offline computer and install it with:

python -m pip install "<file_name>"

Then follow the general cx_Oracle platform installation instructions to install Oracle client libraries.

Install Using GitHub

In order to install using the source on GitHub, use the following commands:

git clone https://github.com/oracle/python-cx_Oracle.git cx_Oracle
cd cx_Oracle
git submodule init
git submodule update
python setup.py install

Note that if you download a source zip file directly from GitHub then you will also need to download an ODPI-C source zip file and extract it inside the directory called “odpi”.

cx_Oracle source code is also available from oss.oracle.com. This can be cloned with:

git clone git://oss.oracle.com/git/oracle/python-cx_Oracle.git cx_Oracle
cd cx_Oracle
git submodule init
git submodule update

Install Using Source from PyPI

The source package can be downloaded manually from PyPI and extracted, after which the following commands should be run:

python setup.py build
python setup.py install

Upgrading from Older Versions

Review the release notes for deprecations and modify any affected code.

If you are upgrading from cx_Oracle 7 note these changes:

If you are upgrading from cx_Oracle 5 note these installation changes:

  • When using Oracle Instant Client, you should not set ORACLE_HOME.
  • On Linux, cx_Oracle 6 and higher no longer uses Instant Client RPMs automatically. You must set LD_LIBRARY_PATH or use ldconfig to locate the Oracle client library.
  • PyPI no longer allows Windows installers or Linux RPMs to be hosted. Use the supplied cx_Oracle Wheels instead, or use RPMs from Oracle, see Installing cx_Oracle RPMs on Oracle Linux.

Installing cx_Oracle in Python 2

To install cx_Oracle in Python 2, use a command like:

python -m pip install cx_Oracle==7.3 --upgrade --user

cx_Oracle 7.3 was the last version with support for Python 2.

For other installation options such as installing through a proxy, see instructions above. Make sure the Oracle Client libraries are in the system library search path because cx_Oracle 7 does not support the cx_Oracle.init_oracle_client() method and does not support loading the Oracle Client libraries from the directory containing the cx_Oracle module binary.

Installing cx_Oracle 5.3

If you require cx_Oracle 5.3, download a Windows installer from PyPI or use python -m pip install cx-oracle==5.3 to install from source.

Very old versions of cx_Oracle can be found in the files section at SourceForce.

Troubleshooting

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 set the environment variables http_proxy and/or https_proxy? Or try pip install --proxy=http://proxy.example.com:80 cx_Oracle --upgrade?
  • If upgrading gave no errors but the old version is still installed, try pip install cx_Oracle --upgrade --force-reinstall
  • If you do not have access to modify your system version of Python, can you use pip install cx_Oracle --upgrade --user or venv?
  • Do you get the error “No module named pip”? The pip module is builtin to Python but is sometimes removed by the OS. Use the venv module (builtin to Python 3.x) or virtualenv module instead.
  • Do you get the error “fatal error: dpi.h: No such file or directory” when building from source code? Ensure that your source installation has a subdirectory called “odpi” containing files. If missing, review the section on Install Using GitHub.

If using cx_Oracle fails:

  • Do you get the error “DPI-1047: Oracle Client library cannot be loaded”?
    • Check that Python, cx_Oracle and your Oracle Client libraries are all 64-bit or all 32-bit. The DPI-1047 message will tell you whether the 64-bit or 32-bit Oracle Client is needed for your Python.
    • On Windows, if you used init_oracle_client() and have a full database installation, make sure this database is the currently configured database.
    • On Windows, if you are not using init_oracle_client(), then restart your command prompt and use set PATH to check the environment variable has the correct Oracle Client listed before any other Oracle directories.
    • On Windows, use the DIR command to verify that OCI.DLL exists in the directory passed to init_oracle_client() or set in PATH.
    • On Windows, check that the correct Windows Redistributables have been installed.
    • On Linux, check the LD_LIBRARY_PATH environment variable contains the Oracle Client library directory. If you are using Oracle Instant Client, a preferred alternative is to ensure a file in the /etc/ld.so.conf.d directory contains the path to the Instant Client directory, and then run ldconfig.
    • On macOS, make sure you are not using the bundled Python (use Homebrew or Python.org instead). If you are not using init_oracle_client(), then put the Oracle Instant Client libraries in ~/lib or /usr/local/lib.
  • If you got “DPI-1072: the Oracle Client library version is unsupported”, then review the installation requirements. cx_Oracle needs Oracle client libraries 11.2 or later. Note that version 19 is not supported on Windows 7. Similar steps shown above for DPI-1047 may help.
  • If you have multiple versions of Python installed, make sure you are using the correct python and pip (or python3 and pip3) executables.