64-bit cx_Oracle: DLL load failed

Question

Using Windows 2008 R2 Server. Server was completely clean. Installed 64-bit Python 3.5, 64-bit Oracle Instant Client 12c. pip installed cx_Oracle successfully. When I try to run a python script that imports cx_Oracle however, I get:

ImportError: DLL load failed: The specified module could not be found.

The instant client path is in the PATH environmental variable. I also made another system variable called ORACLE_HOME with the same instant client path.

I've double checked everything is 64-bit, and looked through SO at the many other times this has come up, and no answer has helped.

Answer 1

First, the environment variable ORACLE_HOME should not be set when an instant client is used. Setting it can have unintended side effects!

Second, if you used pip to install cx_Oracle that suggests you have a compiler and it succeeded in compiling the module. Check to make sure that it used the correct libraries.

Third, you can also download and install a pre-built binary from the PyPI site and see if that helps matters any. Make sure you pick the Python 3.5, 64-bit, Oracle 12c version that is listed there. The PyPI site link is here:

https://pypi.python.org/pypi/cx_Oracle