countdown is simple delay before continuing the program' execution this can also be used for other applications and featuressuch as the followinguse time sleep(to give the user chance to press ctrl- to cancel an actionsuch as deleting files your program can print "press ctrl- to cancelmessage and then handle any keyboardinterrupt exceptions with try and except statements for long-term countdownyou can use timedelta objects to measure the number of dayshoursminutesand seconds until some point ( birthdayan anniversary?in the future summary the unix epoch (january at midnightutcis standard reference time for many programming languagesincluding python while the time time(function module returns an epoch timestamp (that isa float value of the number of seconds since the unix epoch)the datetime module is better for performing date arithmetic and formatting or parsing strings with date information the time sleep(function will block (that isnot returnfor certain number of seconds it can be used to add pauses to your program but if you want to schedule your programs to start at certain timethe instructions at the threading module is used to create multiple threadswhich is useful when you need to download multiple files or do other tasks simultaneously but make sure the thread reads and writes only local variablesor you might run into concurrency issues finallyyour python programs can launch other applications with the subprocess popen(function command line arguments can be passed to the popen(call to open specific documents with the application alternativelyyou can use the startopenor see program with popen(to use your computer' file associations to automatically figure out which application to use to open document by using the other applications on your computeryour python programs can leverage their capabilities for your automation needs practice questions what is the unix epochwhat function returns the number of seconds since the unix epochhow can you pause your program for exactly seconds