macOS Help building python module from dylib

I am trying to do on a mac what I do on linux. Being new to the mac I thought it would be easy but I'm stuck. I use swig to build python modules from c and fortran libraries. It works very well on linux but python requires the use of a shared library and the mac fortran library is a dylib. Anybody know how to convert the fortran dylib to a shared object or any other work around.

Thanks
Tim