sys.prefix

prefix

A string giving the site-specific directory prefix where the platform independent Python files are installed; by default, this is the string '/usr/local'. This can be set at build time with the —prefix argument to the configure script. The main collection of Python library modules is installed in the directory `prefix + ‘/lib/pythonversion’` while the platform independent header files (all except pyconfig.h) are stored in prefix + '/include/pythonversion', where version is equal to version[:3].