code: def find_program (program):
      
      if os.name == 'nt':
          # Add some well-known archiver programs to the search path
          path = os.environ['PATH']
          path = append_to_path(path, get_nt_7z_dir())
          path = append_to_path(path, get_nt_mac_dir())
          path = append_to_path(path, get_nt_winrar_dir())
      else:
          # use default path
          path = None
      return which(program, path=path)
docs: Look for program in environment PATH variable.