The last stop on our widget tour is the most unique. Tkinter also comes with a handful of tools that have to do with the event-driven programming model, not graphics displayed on a computer screen.
Some GUI applications need to perform background activities periodically. For example, to “blink” a widget’s appearance, we’d like to register a callback handler to be invoked at regular time intervals. Similarly, it’s not a good idea to let a long-running file operation block other activity in a GUI; if the event loop could be forced to update periodically, the GUI could remain responsive. Tkinter comes with tools for both scheduling such delayed actions and forcing screen updates:
This tool schedules the function to be called after a number of
function can be any callable Python
object: a function, bound method, etc. This form of the call does not
pause the program -- the callback function is run later from the
normal Tkinter event loop. The milliseconds value can be a floating
point number, to specify fractions of a second. This returns an ID
which can be passed to
after_cancel to cancel the
callback. Since this method is so commonly used, I’ll say more
about it by example in a moment.
This tool pauses the program for a number of milliseconds. For example, an argument of 5000 pauses for 5 seconds. This is essentially the same as Python’s library function ...