After

Tkinter is single-threaded: long work blocks the event loop and freezes the UI. The after methods schedule callbacks to run later on the event loop, which is how you defer work, poll, or animate without threads. To run genuinely blocking work off the main thread and marshal the result back, see Run background work.

The canonical upstream reference is the Tcl after manual page (Tcl 8.6).

after(ms, func=None, *args)

Schedule func(*args) to run once, after ms milliseconds, on the event loop.

Parameters:

• ms (int) – delay in milliseconds.

• func – the callback; if omitted, after simply sleeps ms.

• args – positional arguments passed to func.

Returns:

an id that can be passed to after_cancel (when func is given).

Return type:

str

after_idle(func, *args)

Schedule func(*args) to run once the event loop next becomes idle (after pending events are processed).

Parameters:

• func – the callback.

• args – positional arguments passed to func.

Returns:

an id that can be passed to after_cancel.

Return type:

str

after_cancel(id)

Cancel a callback previously scheduled with after or after_idle.

Parameters:

id – the id returned by the scheduling call.

Returns:

None.

after_info(id=None)

Report the callbacks scheduled with after/after_idle that have not yet run — useful when tracking down a timer that outlives the widget it updates.

Parameters:

id – an optional scheduling id to ask about.

Returns:

with no argument, the ids of all pending callbacks; with an id, that callback’s (script, type), where type is "timer" or "idle".

Return type:

tuple