From: Raymond Hettinger <python@rcn.com>
Date: Thu, 17 Jan 2008 22:27:49 +0000 (+0000)
Subject: Add advice on choosing between scheduler and threading.Timer().
X-Git-Tag: v2.6a1~573
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d0ab014b5ef28a94d69cc70f9d13309c54123d18;p=python

Add advice on choosing between scheduler and threading.Timer().
---

diff --git a/Doc/library/sched.rst b/Doc/library/sched.rst
index 1007cfbc87..e9619fb984 100644
--- a/Doc/library/sched.rst
+++ b/Doc/library/sched.rst
@@ -41,6 +41,31 @@ Example::
    From print_time 930343700.273
    930343700.276
 
+In multi-threaded environments, the :class:`scheduler` class has limitations
+with respect to thread-safety, inability to insert a new task before 
+the one currently pending in a running scheduler, and holding-up the main
+thread until the event queue is empty.  Instead, the preferred approach
+is to use the :class:`threading.Timer` class instead.
+
+Example::
+
+    >>> import time
+    >>> from threading import Timer
+    >>> def print_time():
+    ...     print "From print_time", time.time()
+    ...
+    >>> def print_some_times():
+    ...     print time.time()
+    ...     Timer(5, print_time, ()).start()
+    ...     Timer(10, 1, print_time, ())
+    ...     print time.time()     # executes before the time-delay events 
+    ...
+    >>> print_some_times()
+    930343690.257
+    930343690.301
+    From print_time 930343695.274
+    From print_time 930343700.273
+
 
 .. _scheduler-objects: