Error installing mpi4py with pip on macOS

[jik yan]

I think some environment variables is disable in my OS, so those vars should be xcrun was be direct to /usr/local/bin/mpicc

My python3.7 was installed by pkg from python.org, And I can install *'whl by pip, here some result of cmds

>>which mpicc
/usr/local/bin/mpicc

>>python3 -c "import sysconfig; print(sysconfig.get_config_var('CC'))"
xcrun -sdk macosx clang -arch x86_64

>>python3 -c "import sysconfig; print(sysconfig.get_config_var('LDSHARED'))"
xcrun -sdk macosx clang -arch x86_64 -bundle -undefined dynamic_lookup

[jik yan]

I see the answer at #172