accessing - handling messages nltk suite nntp (network news transfer protocol) - nntplib module - numeric tools numpy programming extension object references callback handlers as deferring calls - object relational mappers (see ormsobject request broker (orb) object typesstoring in shelves object-oriented databases (oodbs) object-oriented programming (see oopobjects callable - - changing classes converting to strings pickled - sharing between pages - shelve constraints offline processingpymailgui program onsignal handler function oodbs (object-oriented databases) oop (object-oriented programmingadding behavior adding inheritance adding persistence - alternative database options class considerations - gui considerations - programming considerations - refactoring code - open function buffering policy functionality modes supported open source software opening files optimization in-place list modifications - moving sets to dictionaries - tuple tree stacks - optionmenu widget class optparse module orb (object request broker) orms (object relational mappersdatabase options functionality - os module administrative tools chdir function chmod function close function dup function dup function environ mapping accessing environment variables accessing shell variables changing shell variables env object functionality execl function execle function execlp function - execlpe function execv function execve function execvp function execvpe function _exit function fdopen function file tools supported fork function functionality os execlp combination - redirecting streams forking tools functionality getcwd function getenv function getpid function kill function linesep character listdir function fetching list of remote files handling unicode filenames joining files printing unicode filenames storing local files walking directory trees walking one directory index