Can you give a test case demonstrating what is not working?  The Python interpreters installed with python.org 10.6+ installers are built to work with all versions of macOS from 10.6 on and should be able to build extension modules with either gcc or clang as provided by the Xcode or Command Line Tools appropriate for the macOS version in use.  And, AFAIK, Python itself has no dependency on C++ at all so there should not be a c++ runtime library conflict due to Python itself.  Although the initial value of the configuration variables are CC=gcc-4.2 and GXX=g++-4.2, when the first compilation of an extension module is attempted, Distutils via Lib/_osx_support.py will do some work to figure out what compilers are available and modify CC and CXX accordingly.  So, for example, on say a macOS 10.13 system with the default Command Line Tools, it should use gcc and g++ which are both aliases for clang.  And, if necessary, you can always override the default compiler selection by explicitly setting the CC and/or CXX environment variables when invoking python.  At least that's how it's supposed to work!