Index: Lib/threading.py
===================================================================
--- Lib/threading.py	(revision 54211)
+++ Lib/threading.py	(arbetskopia)
@@ -625,6 +625,64 @@
             self.function(*self.args, **self.kwargs)
         self.finished.set()
 
+# Periodic timer class
+class PeriodicTimer(Thread):
+    """
+    Periodically call a function.
+
+    PeriodicTimers are, like threads, started by calling their start()
+    method. They can attempt to be cancelled by calling their cancel()
+    method.
+
+    PeriodicTimers use fixed-delay execution which means that the
+    dealy between each invokation of the function is fixed. Because
+    the execution time of the function is not accounted for, the
+    periods therefore become more and more distorted in relation to
+    real time. That makes PeriodicTimers unsuitable for long running
+    threads in which it is critical that each function call time is
+    accurate.
+
+    Example:
+
+        def hello():
+            print "Hi there!"
+
+        t = PeriodicTimer(5, hello)
+        t.start()    # "Hi there!" will be printed every five seconds.
+        
+    """
+    def __init__(self, interval, function, *args, **kwargs):
+        """
+        Create a PeriodicTimer that will continuously call function
+        with arguments args and keyword arguments kwargs, after
+        interval seconds have passed.
+        """
+        Thread.__init__(self)
+        self.interval = interval
+        self.function = function
+        self.args = args
+        self.kwargs = kwargs
+        self.finished = Event()
+
+    def cancel(self):
+        """
+        Make a best effort attempt to stop the PeriodicTimer.
+
+        If the thread is currently executing the function, this effort
+        may not immidiately succeed. The PeriodicTimer is then stopped
+        when execution returns from the function. If the function
+        never returns, the thread will not be stopped.
+        """
+        self.finished.set()
+
+    def run(self):
+        while True:
+            self.finished.wait(self.interval)
+            if self.finished.isSet():
+                break
+            self.function(*self.args, **self.kwargs)
+        
+
 # Special thread class to represent the main thread
 # This is garbage collected through an exit handler