Time Tools, Threads, and Animation
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:
milliseconds, function, *args
This tool schedules the function to be called after a number of milliseconds.
functioncan be any callable Python object: a function, bound method, and so on. This form of the call does not pause the program—the callback function is run later from the normal Tkinter event loop. The
millisecondsvalue can be a floating-point number, to specify fractions of a second. This returns an ID that can be passed to
after_cancelto 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 5,000 pauses for 5 seconds. This is essentially the same as Python’s library function,