Issue #6064: Add a `daemon` keyword argument to the threading.Thread
and multiprocessing.Process constructors in order to override the
default behaviour of inheriting the daemonic property from the current
thread/process.
diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index cc40a2a..9bdbf54 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -297,7 +297,7 @@
:class:`Process` and exceptions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-.. class:: Process([group[, target[, name[, args[, kwargs]]]]])
+.. class:: Process([group[, target[, name[, args[, kwargs]]]]], *, daemon=None)
Process objects represent activity that is run in a separate process. The
:class:`Process` class has equivalents of all the methods of
@@ -312,13 +312,19 @@
:sub:`1`,N\ :sub:`2`,...,N\ :sub:`k` is a sequence of integers whose length
is determined by the *generation* of the process. *args* is the argument
tuple for the target invocation. *kwargs* is a dictionary of keyword
- arguments for the target invocation. By default, no arguments are passed to
- *target*.
+ arguments for the target invocation. If provided, the keyword-only *daemon* argument
+ sets the process :attr:`daemon` flag to ``True`` or ``False``. If ``None``
+ (the default), this flag will be inherited from the creating process.
+
+ By default, no arguments are passed to *target*.
If a subclass overrides the constructor, it must make sure it invokes the
base class constructor (:meth:`Process.__init__`) before doing anything else
to the process.
+ .. versionchanged:: 3.3
+ Added the *daemon* argument.
+
.. method:: run()
Method representing the process's activity.
diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index 5f1b9bf..7d192b5 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -241,7 +241,7 @@
A thread can be flagged as a "daemon thread". The significance of this flag is
that the entire Python program exits when only daemon threads are left. The
initial value is inherited from the creating thread. The flag can be set
-through the :attr:`daemon` property.
+through the :attr:`daemon` property or the *daemon* constructor argument.
There is a "main thread" object; this corresponds to the initial thread of
control in the Python program. It is not a daemon thread.
@@ -254,7 +254,8 @@
impossible to detect the termination of alien threads.
-.. class:: Thread(group=None, target=None, name=None, args=(), kwargs={})
+.. class:: Thread(group=None, target=None, name=None, args=(), kwargs={},
+ verbose=None, *, daemon=None)
This constructor should always be called with keyword arguments. Arguments
are:
@@ -273,10 +274,19 @@
*kwargs* is a dictionary of keyword arguments for the target invocation.
Defaults to ``{}``.
+ *verbose* is a flag used for debugging messages.
+
+ If not ``None``, *daemon* explicitly sets whether the thread is daemonic.
+ If ``None`` (the default), the daemonic property is inherited from the
+ current thread.
+
If the subclass overrides the constructor, it must make sure to invoke the
base class constructor (``Thread.__init__()``) before doing anything else to
the thread.
+ .. versionchanged:: 3.3
+ Added the *daemon* argument.
+
.. method:: start()
Start the thread's activity.
diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py
index b56a061..3fb9ff6 100644
--- a/Lib/multiprocessing/process.py
+++ b/Lib/multiprocessing/process.py
@@ -91,12 +91,16 @@
'''
_Popen = None
- def __init__(self, group=None, target=None, name=None, args=(), kwargs={}):
+ def __init__(self, group=None, target=None, name=None, args=(), kwargs={},
+ *, daemon=None):
assert group is None, 'group argument must be None for now'
count = next(_current_process._counter)
self._identity = _current_process._identity + (count,)
self._authkey = _current_process._authkey
- self._daemonic = _current_process._daemonic
+ if daemon is not None:
+ self._daemonic = daemon
+ else:
+ self._daemonic = _current_process._daemonic
self._tempdir = _current_process._tempdir
self._parent_pid = os.getpid()
self._popen = None
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index 465a831..d154fce 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -163,6 +163,18 @@
self.assertEqual(current.ident, os.getpid())
self.assertEqual(current.exitcode, None)
+ def test_daemon_argument(self):
+ if self.TYPE == "threads":
+ return
+
+ # By default uses the current process's daemon flag.
+ proc0 = self.Process(target=self._test)
+ self.assertEquals(proc0.daemon, self.current_process().daemon)
+ proc1 = self.Process(target=self._test, daemon=True)
+ self.assertTrue(proc1.daemon)
+ proc2 = self.Process(target=self._test, daemon=False)
+ self.assertFalse(proc2.daemon)
+
@classmethod
def _test(cls, q, *args, **kwds):
current = cls.current_process()
diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index ecbbdbf..13a428d 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -427,6 +427,14 @@
t.daemon = True
self.assertTrue('daemon' in repr(t))
+ def test_deamon_param(self):
+ t = threading.Thread()
+ self.assertFalse(t.daemon)
+ t = threading.Thread(daemon=False)
+ self.assertFalse(t.daemon)
+ t = threading.Thread(daemon=True)
+ self.assertTrue(t.daemon)
+
class ThreadJoinOnShutdown(BaseTestCase):
diff --git a/Lib/threading.py b/Lib/threading.py
index fd93f74..cb09afa 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -622,7 +622,7 @@
#XXX __exc_clear = _sys.exc_clear
def __init__(self, group=None, target=None, name=None,
- args=(), kwargs=None, verbose=None):
+ args=(), kwargs=None, verbose=None, *, daemon=None):
assert group is None, "group argument must be None for now"
_Verbose.__init__(self, verbose)
if kwargs is None:
@@ -631,7 +631,10 @@
self._name = str(name or _newname())
self._args = args
self._kwargs = kwargs
- self._daemonic = self._set_daemon()
+ if daemon is not None:
+ self._daemonic = daemon
+ else:
+ self._daemonic = current_thread().daemon
self._ident = None
self._started = Event()
self._stopped = False
@@ -648,10 +651,6 @@
self._block.__init__()
self._started._reset_internal_locks()
- def _set_daemon(self):
- # Overridden in _MainThread and _DummyThread
- return current_thread().daemon
-
def __repr__(self):
assert self._initialized, "Thread.__init__() was not called"
status = "initial"
@@ -948,15 +947,12 @@
class _MainThread(Thread):
def __init__(self):
- Thread.__init__(self, name="MainThread")
+ Thread.__init__(self, name="MainThread", daemon=False)
self._started.set()
self._set_ident()
with _active_limbo_lock:
_active[self._ident] = self
- def _set_daemon(self):
- return False
-
def _exitfunc(self):
self._stop()
t = _pickSomeNonDaemonThread()
@@ -988,7 +984,7 @@
class _DummyThread(Thread):
def __init__(self):
- Thread.__init__(self, name=_newname("Dummy-%d"))
+ Thread.__init__(self, name=_newname("Dummy-%d"), daemon=True)
# Thread._block consumes an OS-level locking primitive, which
# can never be used by a _DummyThread. Since a _DummyThread
@@ -1000,9 +996,6 @@
with _active_limbo_lock:
_active[self._ident] = self
- def _set_daemon(self):
- return True
-
def join(self, timeout=None):
assert False, "cannot join a dummy thread"
diff --git a/Misc/NEWS b/Misc/NEWS
index 99ccbd3..89a8bdb 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -35,6 +35,11 @@
Library
-------
+- Issue #6064: Add a ``daemon`` keyword argument to the threading.Thread
+ and multiprocessing.Process constructors in order to override the
+ default behaviour of inheriting the daemonic property from the current
+ thread/process.
+
- Issue #10956: Buffered I/O classes retry reading or writing after a signal
has arrived and the handler returned successfully.