# HG changeset patch
# User "Denver Coneybeare" <denver@sleepydragon.org>
# Date 1363391909 14400
# Node ID 2541669778fe27dd036253582e6347de4c2821b7
# Parent  b49971a1e70dca77cbd64e1ac3c256e719ef26ca
Replaced the mutable argument defaults [] and {} in threading.Timer.__init__() to None, which is immutable

diff -r b49971a1e70d -r 2541669778fe Doc/library/threading.rst
--- a/Doc/library/threading.rst	Wed Mar 13 02:27:53 2013 +0200
+++ b/Doc/library/threading.rst	Fri Mar 15 19:58:29 2013 -0400
@@ -839,10 +839,12 @@
    t.start() # after 30 seconds, "hello, world" will be printed
 
 
-.. class:: Timer(interval, function, args=[], kwargs={})
+.. class:: Timer(interval, function, args=None, kwargs=None)
 
    Create a timer that will run *function* with arguments *args* and  keyword
    arguments *kwargs*, after *interval* seconds have passed.
+   If *args* is None (the default) then an empty list will be used.
+   If *kwargs* is None (the default) then an empty dict will be used.
 
    .. versionchanged:: 3.3
       changed from a factory function to a class.
diff -r b49971a1e70d -r 2541669778fe Lib/test/test_threading.py
--- a/Lib/test/test_threading.py	Wed Mar 13 02:27:53 2013 +0200
+++ b/Lib/test/test_threading.py	Fri Mar 15 19:58:29 2013 -0400
@@ -787,6 +787,29 @@
         self.assertEqual(p.returncode, 0, "Unexpected error: " + stderr.decode())
         self.assertEqual(data, expected_output)
 
+class TimerTests(BaseTestCase):
+
+    def setUp(self):
+        BaseTestCase.setUp(self)
+        self.callback_invocations = []
+        self.callback_event = threading.Event()
+
+    def test_init_immutable_default_args(self):
+        timer1 = threading.Timer(1, self._callback_spy)
+        timer1.args.append("blah")
+        timer1.kwargs["foo"] = "bar"
+        timer2 = threading.Timer(1, self._callback_spy)
+        timer2.start()
+        self.callback_event.wait()
+        self.assertEquals(len(self.callback_invocations), 1)
+        (invocation_args, invocation_kwargs) = self.callback_invocations[0]
+        self.assertEquals(invocation_args, ())
+        self.assertEquals(invocation_kwargs, {})
+
+    def _callback_spy(self, *args, **kwargs):
+        self.callback_invocations.append((args, kwargs))
+        self.callback_event.set()
+
 class LockTests(lock_tests.LockTests):
     locktype = staticmethod(threading.Lock)
 
diff -r b49971a1e70d -r 2541669778fe Lib/threading.py
--- a/Lib/threading.py	Wed Mar 13 02:27:53 2013 +0200
+++ b/Lib/threading.py	Fri Mar 15 19:58:29 2013 -0400
@@ -808,17 +808,17 @@
 class Timer(Thread):
     """Call a function after a specified number of seconds:
 
-    t = Timer(30.0, f, args=[], kwargs={})
+    t = Timer(30.0, f, args=None, kwargs=None)
     t.start()
     t.cancel() # stop the timer's action if it's still waiting
     """
 
-    def __init__(self, interval, function, args=[], kwargs={}):
+    def __init__(self, interval, function, args=None, kwargs=None):
         Thread.__init__(self)
         self.interval = interval
         self.function = function
-        self.args = args
-        self.kwargs = kwargs
+        self.args = args if args is not None else []
+        self.kwargs = kwargs if kwargs is not None else {}
         self.finished = Event()
 
     def cancel(self):