bpo-32839: Add the after_info() method for Tkinter widgets (GH-5664)

Lib/test/test_tkinter/test_misc.py

@@ -232,6 +232,46 @@ class MiscTest(AbstractTkTest, unittest.TestCase):
         with self.assertRaises(tkinter.TclError):
             root.tk.call('after', 'info', idle1)
 
+    def test_after_info(self):
+        root = self.root
+
+        # No events.
+        self.assertEqual(root.after_info(), ())
+
+        # Add timer.
+        timer = root.after(1, lambda: 'break')
+
+        # With no parameter, it returns a tuple of the event handler ids.
+        self.assertEqual(root.after_info(), (timer, ))
+        root.after_cancel(timer)
+
+        timer1 = root.after(5000, lambda: 'break')
+        timer2 = root.after(5000, lambda: 'break')
+        idle1 = root.after_idle(lambda: 'break')
+        # Only contains new events and not 'timer'.
+        self.assertEqual(root.after_info(), (idle1, timer2, timer1))
+
+        # With a parameter returns a tuple of (script, type).
+        timer1_info = root.after_info(timer1)
+        self.assertEqual(len(timer1_info), 2)
+        self.assertEqual(timer1_info[1], 'timer')
+        idle1_info = root.after_info(idle1)
+        self.assertEqual(len(idle1_info), 2)
+        self.assertEqual(idle1_info[1], 'idle')
+
+        root.after_cancel(timer1)
+        with self.assertRaises(tkinter.TclError):
+            root.after_info(timer1)
+        root.after_cancel(timer2)
+        with self.assertRaises(tkinter.TclError):
+            root.after_info(timer2)
+        root.after_cancel(idle1)
+        with self.assertRaises(tkinter.TclError):
+            root.after_info(idle1)
+
+        # No events.
+        self.assertEqual(root.after_info(), ())
+
     def test_clipboard(self):
         root = self.root
         root.clipboard_clear()

Lib/tkinter/__init__.py

@@ -897,6 +897,21 @@ class Misc:
             pass
         self.tk.call('after', 'cancel', id)
 
+    def after_info(self, id=None):
+        """Return information about existing event handlers.
+
+        With no argument, return a tuple of the identifiers for all existing
+        event handlers created by the after and after_idle commands for this
+        interpreter.  If id is supplied, it specifies an existing handler; id
+        must have been the return value from some previous call to after or
+        after_idle and it must not have triggered yet or been canceled. If the
+        id doesn't exist, a TclError is raised.  Otherwise, the return value is
+        a tuple containing (script, type) where script is a reference to the
+        function to be called by the event handler and type is either 'idle'
+        or 'timer' to indicate what kind of event handler it is.
+        """
+        return self.tk.splitlist(self.tk.call('after', 'info', id))
+
     def bell(self, displayof=0):
         """Ring a display's bell."""
         self.tk.call(('bell',) + self._displayof(displayof))