[oracle@obi11-01 instantclient_12_1]$ sudo pip install cx_Oracle
Downloading/unpacking cx-Oracle
  Running setup.py egg_info for package cx-Oracle
    Traceback (most recent call last):
      File "<string>", line 16, in <module>
      File "/tmp/pip-build-root/cx-Oracle/setup.py", line 170, in <module>
        raise DistutilsSetupError("cannot locate an Oracle software " \
    distutils.errors.DistutilsSetupError: cannot locate an Oracle software installation
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):

  File "<string>", line 16, in <module>

  File "/tmp/pip-build-root/cx-Oracle/setup.py", line 170, in <module>

    raise DistutilsSetupError("cannot locate an Oracle software " \

distutils.errors.DistutilsSetupError: cannot locate an Oracle software installation

The problem was running as sudo all of the environment variables (ORACLE_HOME etc) were not actually available in the context. As a hack I just chmod'd the target site-packages folder that pip was trying to write to, and ran as the oracle user, not sudo

Also make sure you have instant client basic and sdk.