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authorGeorg Brandl <georg@python.org>2009-07-26 14:48:09 (GMT)
committerGeorg Brandl <georg@python.org>2009-07-26 14:48:09 (GMT)
commit7a72b3ad7b02612254c7e256b8a67ce7ccf7994a (patch)
tree32dadbacf6dd072b83d250202552eda55da9de62 /Doc
parent6730538ed31031e0ef70cf1ec1e4b37f4d1db4ff (diff)
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Recorded merge of revisions 74210 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk ........ r74210 | georg.brandl | 2009-07-26 16:44:23 +0200 (So, 26 Jul 2009) | 1 line Move member descriptions inside the classes. ........
Diffstat (limited to 'Doc')
-rw-r--r--Doc/library/threading.rst323
1 files changed, 153 insertions, 170 deletions
diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index d880157..ce91750 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -1,4 +1,3 @@
-
:mod:`threading` --- Higher-level threading interface
=====================================================
@@ -213,7 +212,8 @@ impossible to detect the termination of alien threads.
.. class:: Thread(group=None, target=None, name=None, args=(), kwargs={})
- This constructor should always be called with keyword arguments. Arguments are:
+ This constructor should always be called with keyword arguments. Arguments
+ are:
*group* should be ``None``; reserved for future extension when a
:class:`ThreadGroup` class is implemented.
@@ -221,111 +221,103 @@ impossible to detect the termination of alien threads.
*target* is the callable object to be invoked by the :meth:`run` method.
Defaults to ``None``, meaning nothing is called.
- *name* is the thread name. By default, a unique name is constructed of the form
- "Thread-*N*" where *N* is a small decimal number.
+ *name* is the thread name. By default, a unique name is constructed of the
+ form "Thread-*N*" where *N* is a small decimal number.
*args* is the argument tuple for the target invocation. Defaults to ``()``.
*kwargs* is a dictionary of keyword arguments for the target invocation.
Defaults to ``{}``.
- 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.
-
-
-.. method:: Thread.start()
-
- Start the thread's activity.
-
- It must be called at most once per thread object. It arranges for the object's
- :meth:`run` method to be invoked in a separate thread of control.
+ 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.
- This method will raise a :exc:`RuntimeException` if called more than once on the
- same thread object.
+ .. method:: start()
+ Start the thread's activity.
-.. method:: Thread.run()
+ It must be called at most once per thread object. It arranges for the
+ object's :meth:`run` method to be invoked in a separate thread of control.
- Method representing the thread's activity.
+ This method will raise a :exc:`RuntimeException` if called more than once
+ on the same thread object.
- You may override this method in a subclass. The standard :meth:`run` method
- invokes the callable object passed to the object's constructor as the *target*
- argument, if any, with sequential and keyword arguments taken from the *args*
- and *kwargs* arguments, respectively.
+ .. method:: run()
+ Method representing the thread's activity.
-.. method:: Thread.join([timeout])
+ You may override this method in a subclass. The standard :meth:`run`
+ method invokes the callable object passed to the object's constructor as
+ the *target* argument, if any, with sequential and keyword arguments taken
+ from the *args* and *kwargs* arguments, respectively.
- Wait until the thread terminates. This blocks the calling thread until the
- thread whose :meth:`join` method is called terminates -- either normally or
- through an unhandled exception -- or until the optional timeout occurs.
+ .. method:: join([timeout])
- When the *timeout* argument is present and not ``None``, it should be a floating
- point number specifying a timeout for the operation in seconds (or fractions
- thereof). As :meth:`join` always returns ``None``, you must call :meth:`is_alive`
- after :meth:`join` to decide whether a timeout happened -- if the thread is
- still alive, the :meth:`join` call timed out.
+ Wait until the thread terminates. This blocks the calling thread until the
+ thread whose :meth:`join` method is called terminates -- either normally
+ or through an unhandled exception -- or until the optional timeout occurs.
- When the *timeout* argument is not present or ``None``, the operation will block
- until the thread terminates.
+ When the *timeout* argument is present and not ``None``, it should be a
+ floating point number specifying a timeout for the operation in seconds
+ (or fractions thereof). As :meth:`join` always returns ``None``, you must
+ call :meth:`is_alive` after :meth:`join` to decide whether a timeout
+ happened -- if the thread is still alive, the :meth:`join` call timed out.
- A thread can be :meth:`join`\ ed many times.
+ When the *timeout* argument is not present or ``None``, the operation will
+ block until the thread terminates.
- :meth:`join` raises a :exc:`RuntimeError` if an attempt is made to join
- the current thread as that would cause a deadlock. It is also an error to
- :meth:`join` a thread before it has been started and attempts to do so
- raises the same exception.
+ A thread can be :meth:`join`\ ed many times.
+ :meth:`join` raises a :exc:`RuntimeError` if an attempt is made to join
+ the current thread as that would cause a deadlock. It is also an error to
+ :meth:`join` a thread before it has been started and attempts to do so
+ raises the same exception.
-.. attribute:: Thread.name
+ .. attribute:: name
- A string used for identification purposes only. It has no semantics.
- Multiple threads may be given the same name. The initial name is set by the
- constructor.
+ A string used for identification purposes only. It has no semantics.
+ Multiple threads may be given the same name. The initial name is set by
+ the constructor.
+ .. method:: getName()
+ setName()
-.. method:: Thread.getName()
- Thread.setName()
+ Old getter/setter API for :attr:`~Thread.name`; use it directly as a
+ property instead.
- Old getter/setter API for :attr:`~Thread.name`; use it directly as a property
- instead.
+ .. attribute:: ident
+ The 'thread identifier' of this thread or ``None`` if the thread has not
+ been started. This is a nonzero integer. See the
+ :func:`thread.get_ident()` function. Thread identifiers may be recycled
+ when a thread exits and another thread is created. The identifier is
+ available even after the thread has exited.
-.. attribute:: Thread.ident
+ .. method:: is_alive()
- The 'thread identifier' of this thread or ``None`` if the thread has not been
- started. This is a nonzero integer. See the :func:`thread.get_ident()`
- function. Thread identifiers may be recycled when a thread exits and another
- thread is created. The identifier is available even after the thread has
- exited.
+ Return whether the thread is alive.
+ Roughly, a thread is alive from the moment the :meth:`start` method
+ returns until its :meth:`run` method terminates. The module function
+ :func:`enumerate` returns a list of all alive threads.
-.. method:: Thread.is_alive()
+ .. attribute:: daemon
- Return whether the thread is alive.
+ A boolean value indicating whether this thread is a daemon thread (True)
+ or not (False). This must be set before :meth:`start` is called,
+ otherwise :exc:`RuntimeError` is raised. Its initial value is inherited
+ from the creating thread; the main thread is not a daemon thread and
+ therefore all threads created in the main thread default to :attr:`daemon`
+ = ``False``.
- Roughly, a thread is alive from the moment the :meth:`start` method returns
- until its :meth:`run` method terminates. The module function :func:`enumerate`
- returns a list of all alive threads.
+ The entire Python program exits when no alive non-daemon threads are left.
+ .. method:: isDaemon()
+ setDaemon()
-.. attribute:: Thread.daemon
-
- A boolean value indicating whether this thread is a daemon thread (True) or
- not (False). This must be set before :meth:`start` is called, otherwise
- :exc:`RuntimeError` is raised. Its initial value is inherited from the
- creating thread; the main thread is not a daemon thread and therefore all
- threads created in the main thread default to :attr:`daemon` = ``False``.
-
- The entire Python program exits when no alive non-daemon threads are left.
-
-
-.. method:: Thread.isDaemon()
- Thread.setDaemon()
-
- Old getter/setter API for :attr:`~Thread.daemon`; use it directly as a
- property instead.
+ Old getter/setter API for :attr:`~Thread.daemon`; use it directly as a
+ property instead.
.. _lock-objects:
@@ -496,69 +488,66 @@ needs to wake up one consumer thread.
.. class:: Condition([lock])
- If the *lock* argument is given and not ``None``, it must be a :class:`Lock` or
- :class:`RLock` object, and it is used as the underlying lock. Otherwise, a new
- :class:`RLock` object is created and used as the underlying lock.
-
+ If the *lock* argument is given and not ``None``, it must be a :class:`Lock`
+ or :class:`RLock` object, and it is used as the underlying lock. Otherwise,
+ a new :class:`RLock` object is created and used as the underlying lock.
-.. method:: Condition.acquire(*args)
+ .. method:: acquire(*args)
- Acquire the underlying lock. This method calls the corresponding method on the
- underlying lock; the return value is whatever that method returns.
+ Acquire the underlying lock. This method calls the corresponding method on
+ the underlying lock; the return value is whatever that method returns.
+ .. method:: release()
-.. method:: Condition.release()
+ Release the underlying lock. This method calls the corresponding method on
+ the underlying lock; there is no return value.
- Release the underlying lock. This method calls the corresponding method on the
- underlying lock; there is no return value.
+ .. method:: wait([timeout])
+ Wait until notified or until a timeout occurs. If the calling thread has
+ not acquired the lock when this method is called, a :exc:`RuntimeError` is
+ raised.
-.. method:: Condition.wait([timeout])
+ This method releases the underlying lock, and then blocks until it is
+ awakened by a :meth:`notify` or :meth:`notify_all` call for the same
+ condition variable in another thread, or until the optional timeout
+ occurs. Once awakened or timed out, it re-acquires the lock and returns.
- Wait until notified or until a timeout occurs. If the calling thread has not
- acquired the lock when this method is called, a :exc:`RuntimeError` is raised.
+ When the *timeout* argument is present and not ``None``, it should be a
+ floating point number specifying a timeout for the operation in seconds
+ (or fractions thereof).
- This method releases the underlying lock, and then blocks until it is awakened
- by a :meth:`notify` or :meth:`notify_all` call for the same condition variable in
- another thread, or until the optional timeout occurs. Once awakened or timed
- out, it re-acquires the lock and returns.
+ When the underlying lock is an :class:`RLock`, it is not released using
+ its :meth:`release` method, since this may not actually unlock the lock
+ when it was acquired multiple times recursively. Instead, an internal
+ interface of the :class:`RLock` class is used, which really unlocks it
+ even when it has been recursively acquired several times. Another internal
+ interface is then used to restore the recursion level when the lock is
+ reacquired.
- When the *timeout* argument is present and not ``None``, it should be a floating
- point number specifying a timeout for the operation in seconds (or fractions
- thereof).
+ .. method:: notify()
- When the underlying lock is an :class:`RLock`, it is not released using its
- :meth:`release` method, since this may not actually unlock the lock when it was
- acquired multiple times recursively. Instead, an internal interface of the
- :class:`RLock` class is used, which really unlocks it even when it has been
- recursively acquired several times. Another internal interface is then used to
- restore the recursion level when the lock is reacquired.
+ Wake up a thread waiting on this condition, if any. If the calling thread
+ has not acquired the lock when this method is called, a
+ :exc:`RuntimeError` is raised.
+ This method wakes up one of the threads waiting for the condition
+ variable, if any are waiting; it is a no-op if no threads are waiting.
-.. method:: Condition.notify()
+ The current implementation wakes up exactly one thread, if any are
+ waiting. However, it's not safe to rely on this behavior. A future,
+ optimized implementation may occasionally wake up more than one thread.
- Wake up a thread waiting on this condition, if any. If the calling thread
- has not acquired the lock when this method is called, a :exc:`RuntimeError`
- is raised.
+ Note: the awakened thread does not actually return from its :meth:`wait`
+ call until it can reacquire the lock. Since :meth:`notify` does not
+ release the lock, its caller should.
- This method wakes up one of the threads waiting for the condition variable,
- if any are waiting; it is a no-op if no threads are waiting.
+ .. method:: notify_all()
- The current implementation wakes up exactly one thread, if any are waiting.
- However, it's not safe to rely on this behavior. A future, optimized
- implementation may occasionally wake up more than one thread.
-
- Note: the awakened thread does not actually return from its :meth:`wait` call
- until it can reacquire the lock. Since :meth:`notify` does not release the
- lock, its caller should.
-
-
-.. method:: Condition.notify_all()
-
- Wake up all threads waiting on this condition. This method acts like
- :meth:`notify`, but wakes up all waiting threads instead of one. If the calling
- thread has not acquired the lock when this method is called, a
- :exc:`RuntimeError` is raised.
+ Wake up all threads waiting on this condition. This method acts like
+ :meth:`notify`, but wakes up all waiting threads instead of one. If the
+ calling thread has not acquired the lock when this method is called, a
+ :exc:`RuntimeError` is raised.
.. _semaphore-objects:
@@ -582,33 +571,31 @@ waiting until some other thread calls :meth:`release`.
defaults to ``1``. If the *value* given is less than 0, :exc:`ValueError` is
raised.
+ .. method:: acquire([blocking])
-.. method:: Semaphore.acquire([blocking])
-
- Acquire a semaphore.
-
- When invoked without arguments: if the internal counter is larger than zero on
- entry, decrement it by one and return immediately. If it is zero on entry,
- block, waiting until some other thread has called :meth:`release` to make it
- larger than zero. This is done with proper interlocking so that if multiple
- :meth:`acquire` calls are blocked, :meth:`release` will wake exactly one of them
- up. The implementation may pick one at random, so the order in which blocked
- threads are awakened should not be relied on. There is no return value in this
- case.
+ Acquire a semaphore.
- When invoked with *blocking* set to true, do the same thing as when called
- without arguments, and return true.
+ When invoked without arguments: if the internal counter is larger than
+ zero on entry, decrement it by one and return immediately. If it is zero
+ on entry, block, waiting until some other thread has called
+ :meth:`release` to make it larger than zero. This is done with proper
+ interlocking so that if multiple :meth:`acquire` calls are blocked,
+ :meth:`release` will wake exactly one of them up. The implementation may
+ pick one at random, so the order in which blocked threads are awakened
+ should not be relied on. There is no return value in this case.
- When invoked with *blocking* set to false, do not block. If a call without an
- argument would block, return false immediately; otherwise, do the same thing as
- when called without arguments, and return true.
+ When invoked with *blocking* set to true, do the same thing as when called
+ without arguments, and return true.
+ When invoked with *blocking* set to false, do not block. If a call
+ without an argument would block, return false immediately; otherwise, do
+ the same thing as when called without arguments, and return true.
-.. method:: Semaphore.release()
+ .. method:: release()
- Release a semaphore, incrementing the internal counter by one. When it was zero
- on entry and another thread is waiting for it to become larger than zero again,
- wake up that thread.
+ Release a semaphore, incrementing the internal counter by one. When it
+ was zero on entry and another thread is waiting for it to become larger
+ than zero again, wake up that thread.
.. _semaphore-examples:
@@ -655,40 +642,37 @@ An event object manages an internal flag that can be set to true with the
The internal flag is initially false.
+ .. method:: is_set()
-.. method:: Event.is_set()
+ Return true if and only if the internal flag is true.
- Return true if and only if the internal flag is true.
+ .. method:: set()
+ Set the internal flag to true. All threads waiting for it to become true
+ are awakened. Threads that call :meth:`wait` once the flag is true will
+ not block at all.
-.. method:: Event.set()
+ .. method:: clear()
- Set the internal flag to true. All threads waiting for it to become true are
- awakened. Threads that call :meth:`wait` once the flag is true will not block at
- all.
+ Reset the internal flag to false. Subsequently, threads calling
+ :meth:`wait` will block until :meth:`set` is called to set the internal
+ flag to true again.
+ .. method:: wait([timeout])
-.. method:: Event.clear()
+ Block until the internal flag is true. If the internal flag is true on
+ entry, return immediately. Otherwise, block until another thread calls
+ :meth:`set` to set the flag to true, or until the optional timeout occurs.
- Reset the internal flag to false. Subsequently, threads calling :meth:`wait`
- will block until :meth:`set` is called to set the internal flag to true again.
+ When the timeout argument is present and not ``None``, it should be a
+ floating point number specifying a timeout for the operation in seconds
+ (or fractions thereof).
+ This method returns the internal flag on exit, so it will always return
+ ``True`` except if a timeout is given and the operation times out.
-.. method:: Event.wait([timeout])
-
- Block until the internal flag is true. If the internal flag is true on entry,
- return immediately. Otherwise, block until another thread calls :meth:`set`
- to set the flag to true, or until the optional timeout occurs.
-
- When the timeout argument is present and not ``None``, it should be a floating
- point number specifying a timeout for the operation in seconds (or fractions
- thereof).
-
- This method returns the internal flag on exit, so it will always return
- ``True`` except if a timeout is given and the operation times out.
-
- .. versionchanged:: 3.1
- Previously, the method always returned ``None``.
+ .. versionchanged:: 3.1
+ Previously, the method always returned ``None``.
.. _timer-objects:
@@ -719,11 +703,10 @@ For example::
Create a timer that will run *function* with arguments *args* and keyword
arguments *kwargs*, after *interval* seconds have passed.
+ .. method:: cancel()
-.. method:: Timer.cancel()
-
- Stop the timer, and cancel the execution of the timer's action. This will only
- work if the timer is still in its waiting stage.
+ Stop the timer, and cancel the execution of the timer's action. This will
+ only work if the timer is still in its waiting stage.
.. _with-locks: