built-in functions are actually system interfaces as well--the open functionfor exampleinterfaces with the file system but by and largesys and os together form the core of python' built-in system tools arsenal in principle at leastsys exports components related to the python interpreter itself ( the module search path)and os contains variables and functions that map to the operating system on which python is run in practicethis distinction may not always seem clear-cut ( the standard input and output streams show up in sysbut they are arguably tied to operating system paradigmsthe good news is that you'll soon use the tools in these modules so often that their locations will be permanently stamped on your memory the os module also attempts to provide portable programming interface to the underlying operating systemits functions may be implemented differently on different platformsbut to python scriptsthey look the same everywhere and if that' still not enoughthe os module also exports nested submoduleos pathwhich provides portable interface to file and directory processing tools module documentation sources as you can probably deduce from the preceding paragraphslearning to write system scripts in python is mostly matter of learning about python' system modules luckilythere are variety of information sources to make this task easier--from module attributes to published references and books for instanceif you want to know everything that built-in module exportsyou can read its library manual entrystudy its source code (python is open source softwareafter all)or fetch its attribute list and documentation string interactively let' import sys in python and see what it has to offerc:\pp \systempython import sys dir(sys['__displayhook__''__doc__''__excepthook__''__name__''__package__''__stderr__''__stdin__''__stdout__''_clear_type_cache''_current_frames''_getframe''api_version''argv''builtin_module_names''byteorder''call_tracing''callstats''copyright''displayhook''dllhandle''dont_write_bytecode''exc_info''excepthook''exec_prefix''executable''exit''flags''float_info''float_repr_style''getcheckinterval''getdefaultencoding''getfilesystemencoding''getprofile''getrecursionlimit''getrefcount''getsizeof''gettrace''getwindowsversion''hexversion''int_info''intern''maxsize''maxunicode''meta_path''modules''path''path_hooks''path_importer_cache''platform''prefix''ps ''ps ''setcheckinterval''setfilesystemencoding''setprofile''setrecursionlimit'they may also work their way into your subconscious python newcomers sometimes describe phenomenon in which they "dream in python(insert overly simplistic freudian analysis here system scripting overview