also notice how some of the classes in this example use the sys executable path string to obtain the python executable' full path name this is partly due to their role in userfriendly demo launchers in prior versions that predated sys executablethese classes instead called two functions exported by module named launcher py to find suitable python executableregardless of whether the user had added its directory to the system path variable' setting this search is no longer required since 'll describe this module' other roles in the next and since this search has been largely precluded by python' perpetual pandering to programmersprofessional proclivitiesi'll postpone any pointless pedagogical presentation here (period other system tools coverage that concludes our tour of python system tools in this and the prior three we've met most of the commonly used system tools in the python library along the waywe've also learned how to use them to do useful things such as start programsprocess directoriesand so on the next wraps up this domain by using the tools we've just met to implement scripts that do useful and more realistic system-level work still other system-related tools in python appear later in this text for instancesocketsused to communicate with other programs and networks and introduced briefly hereshow up again in in common gui use case and are covered in full in select callsused to multiplex among tasksare also introduced in as way to implement servers file locking with os openintroduced in is discussed again in conjunction with later examples regular expressionsstring pattern matching used by many text processing tools in the system administration domaindon' appear until moreoverthings like forks and threads are used extensively in the internet scripting see the discussion of threaded guis in and the server implementations in the ftp client gui in and the pymailgui program in along the waywe'll also meet higher-level python modulessuch as socketserverwhich implement fork and thread-based socket server code for us in factmany of the last four tools will pop up constantly in later examples in this book--about what one would expect of general-purpose portable libraries parallel system tools