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+
+:mod:`threading` --- Higher-level threading interface
+=====================================================
+
+.. module:: threading
+ :synopsis: Higher-level threading interface.
+
+
+This module constructs higher-level threading interfaces on top of the lower
+level :mod:`thread` module.
+
+The :mod:`dummy_threading` module is provided for situations where
+:mod:`threading` cannot be used because :mod:`thread` is missing.
+
+This module defines the following functions and objects:
+
+
+.. function:: activeCount()
+
+ Return the number of :class:`Thread` objects currently alive. The returned
+ count is equal to the length of the list returned by :func:`enumerate`.
+
+
+.. function:: Condition()
+ :noindex:
+
+ A factory function that returns a new condition variable object. A condition
+ variable allows one or more threads to wait until they are notified by another
+ thread.
+
+
+.. function:: currentThread()
+
+ Return the current :class:`Thread` object, corresponding to the caller's thread
+ of control. If the caller's thread of control was not created through the
+ :mod:`threading` module, a dummy thread object with limited functionality is
+ returned.
+
+
+.. function:: enumerate()
+
+ Return a list of all :class:`Thread` objects currently alive. The list includes
+ daemonic threads, dummy thread objects created by :func:`currentThread`, and the
+ main thread. It excludes terminated threads and threads that have not yet been
+ started.
+
+
+.. function:: Event()
+ :noindex:
+
+ A factory function that returns a new event object. An event manages a flag
+ that can be set to true with the :meth:`set` method and reset to false with the
+ :meth:`clear` method. The :meth:`wait` method blocks until the flag is true.
+
+
+.. class:: local
+
+ A class that represents thread-local data. Thread-local data are data whose
+ values are thread specific. To manage thread-local data, just create an
+ instance of :class:`local` (or a subclass) and store attributes on it::
+
+ mydata = threading.local()
+ mydata.x = 1
+
+ The instance's values will be different for separate threads.
+
+ For more details and extensive examples, see the documentation string of the
+ :mod:`_threading_local` module.
+
+ .. versionadded:: 2.4
+
+
+.. function:: Lock()
+
+ A factory function that returns a new primitive lock object. Once a thread has
+ acquired it, subsequent attempts to acquire it block, until it is released; any
+ thread may release it.
+
+
+.. function:: RLock()
+
+ A factory function that returns a new reentrant lock object. A reentrant lock
+ must be released by the thread that acquired it. Once a thread has acquired a
+ reentrant lock, the same thread may acquire it again without blocking; the
+ thread must release it once for each time it has acquired it.
+
+
+.. function:: Semaphore([value])
+ :noindex:
+
+ A factory function that returns a new semaphore object. A semaphore manages a
+ counter representing the number of :meth:`release` calls minus the number of
+ :meth:`acquire` calls, plus an initial value. The :meth:`acquire` method blocks
+ if necessary until it can return without making the counter negative. If not
+ given, *value* defaults to 1.
+
+
+.. function:: BoundedSemaphore([value])
+
+ A factory function that returns a new bounded semaphore object. A bounded
+ semaphore checks to make sure its current value doesn't exceed its initial
+ value. If it does, :exc:`ValueError` is raised. In most situations semaphores
+ are used to guard resources with limited capacity. If the semaphore is released
+ too many times it's a sign of a bug. If not given, *value* defaults to 1.
+
+
+.. class:: Thread
+
+ A class that represents a thread of control. This class can be safely
+ subclassed in a limited fashion.
+
+
+.. class:: Timer
+
+ A thread that executes a function after a specified interval has passed.
+
+
+.. function:: settrace(func)
+
+ .. index:: single: trace function
+
+ Set a trace function for all threads started from the :mod:`threading` module.
+ The *func* will be passed to :func:`sys.settrace` for each thread, before its
+ :meth:`run` method is called.
+
+ .. versionadded:: 2.3
+
+
+.. function:: setprofile(func)
+
+ .. index:: single: profile function
+
+ Set a profile function for all threads started from the :mod:`threading` module.
+ The *func* will be passed to :func:`sys.setprofile` for each thread, before its
+ :meth:`run` method is called.
+
+ .. versionadded:: 2.3
+
+
+.. function:: stack_size([size])
+
+ Return the thread stack size used when creating new threads. The optional
+ *size* argument specifies the stack size to be used for subsequently created
+ threads, and must be 0 (use platform or configured default) or a positive
+ integer value of at least 32,768 (32kB). If changing the thread stack size is
+ unsupported, a :exc:`ThreadError` is raised. If the specified stack size is
+ invalid, a :exc:`ValueError` is raised and the stack size is unmodified. 32kB
+ is currently the minimum supported stack size value to guarantee sufficient
+ stack space for the interpreter itself. Note that some platforms may have
+ particular restrictions on values for the stack size, such as requiring a
+ minimum stack size > 32kB or requiring allocation in multiples of the system
+ memory page size - platform documentation should be referred to for more
+ information (4kB pages are common; using multiples of 4096 for the stack size is
+ the suggested approach in the absence of more specific information).
+ Availability: Windows, systems with POSIX threads.
+
+ .. versionadded:: 2.5
+
+Detailed interfaces for the objects are documented below.
+
+The design of this module is loosely based on Java's threading model. However,
+where Java makes locks and condition variables basic behavior of every object,
+they are separate objects in Python. Python's :class:`Thread` class supports a
+subset of the behavior of Java's Thread class; currently, there are no
+priorities, no thread groups, and threads cannot be destroyed, stopped,
+suspended, resumed, or interrupted. The static methods of Java's Thread class,
+when implemented, are mapped to module-level functions.
+
+All of the methods described below are executed atomically.
+
+
+.. _lock-objects:
+
+Lock Objects
+------------
+
+A primitive lock is a synchronization primitive that is not owned by a
+particular thread when locked. In Python, it is currently the lowest level
+synchronization primitive available, implemented directly by the :mod:`thread`
+extension module.
+
+A primitive lock is in one of two states, "locked" or "unlocked". It is created
+in the unlocked state. It has two basic methods, :meth:`acquire` and
+:meth:`release`. When the state is unlocked, :meth:`acquire` changes the state
+to locked and returns immediately. When the state is locked, :meth:`acquire`
+blocks until a call to :meth:`release` in another thread changes it to unlocked,
+then the :meth:`acquire` call resets it to locked and returns. The
+:meth:`release` method should only be called in the locked state; it changes the
+state to unlocked and returns immediately. If an attempt is made to release an
+unlocked lock, a :exc:`RuntimeError` will be raised.
+
+When more than one thread is blocked in :meth:`acquire` waiting for the state to
+turn to unlocked, only one thread proceeds when a :meth:`release` call resets
+the state to unlocked; which one of the waiting threads proceeds is not defined,
+and may vary across implementations.
+
+All methods are executed atomically.
+
+
+.. method:: Lock.acquire([blocking=1])
+
+ Acquire a lock, blocking or non-blocking.
+
+ When invoked without arguments, block until the lock is unlocked, then set it to
+ locked, and return true.
+
+ When invoked with the *blocking* argument set to true, do the same thing as when
+ called without arguments, and return true.
+
+ When invoked with the *blocking* argument 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:: Lock.release()
+
+ Release a lock.
+
+ When the lock is locked, reset it to unlocked, and return. If any other threads
+ are blocked waiting for the lock to become unlocked, allow exactly one of them
+ to proceed.
+
+ Do not call this method when the lock is unlocked.
+
+ There is no return value.
+
+
+.. _rlock-objects:
+
+RLock Objects
+-------------
+
+A reentrant lock is a synchronization primitive that may be acquired multiple
+times by the same thread. Internally, it uses the concepts of "owning thread"
+and "recursion level" in addition to the locked/unlocked state used by primitive
+locks. In the locked state, some thread owns the lock; in the unlocked state,
+no thread owns it.
+
+To lock the lock, a thread calls its :meth:`acquire` method; this returns once
+the thread owns the lock. To unlock the lock, a thread calls its
+:meth:`release` method. :meth:`acquire`/:meth:`release` call pairs may be
+nested; only the final :meth:`release` (the :meth:`release` of the outermost
+pair) resets the lock to unlocked and allows another thread blocked in
+:meth:`acquire` to proceed.
+
+
+.. method:: RLock.acquire([blocking=1])
+
+ Acquire a lock, blocking or non-blocking.
+
+ When invoked without arguments: if this thread already owns the lock, increment
+ the recursion level by one, and return immediately. Otherwise, if another
+ thread owns the lock, block until the lock is unlocked. Once the lock is
+ unlocked (not owned by any thread), then grab ownership, set the recursion level
+ to one, and return. If more than one thread is blocked waiting until the lock
+ is unlocked, only one at a time will be able to grab ownership of the lock.
+ There is no return value in this case.
+
+ When invoked with the *blocking* argument set to true, do the same thing as when
+ called without arguments, and return true.
+
+ When invoked with the *blocking* argument 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:: RLock.release()
+
+ Release a lock, decrementing the recursion level. If after the decrement it is
+ zero, reset the lock to unlocked (not owned by any thread), and if any other
+ threads are blocked waiting for the lock to become unlocked, allow exactly one
+ of them to proceed. If after the decrement the recursion level is still
+ nonzero, the lock remains locked and owned by the calling thread.
+
+ Only call this method when the calling thread owns the lock. A
+ :exc:`RuntimeError` is raised if this method is called when the lock is
+ unlocked.
+
+ There is no return value.
+
+
+.. _condition-objects:
+
+Condition Objects
+-----------------
+
+A condition variable is always associated with some kind of lock; this can be
+passed in or one will be created by default. (Passing one in is useful when
+several condition variables must share the same lock.)
+
+A condition variable has :meth:`acquire` and :meth:`release` methods that call
+the corresponding methods of the associated lock. It also has a :meth:`wait`
+method, and :meth:`notify` and :meth:`notifyAll` methods. These three must only
+be called when the calling thread has acquired the lock, otherwise a
+:exc:`RuntimeError` is raised.
+
+The :meth:`wait` method releases the lock, and then blocks until it is awakened
+by a :meth:`notify` or :meth:`notifyAll` call for the same condition variable in
+another thread. Once awakened, it re-acquires the lock and returns. It is also
+possible to specify a timeout.
+
+The :meth:`notify` method wakes up one of the threads waiting for the condition
+variable, if any are waiting. The :meth:`notifyAll` method wakes up all threads
+waiting for the condition variable.
+
+Note: the :meth:`notify` and :meth:`notifyAll` methods don't release the lock;
+this means that the thread or threads awakened will not return from their
+:meth:`wait` call immediately, but only when the thread that called
+:meth:`notify` or :meth:`notifyAll` finally relinquishes ownership of the lock.
+
+Tip: the typical programming style using condition variables uses the lock to
+synchronize access to some shared state; threads that are interested in a
+particular change of state call :meth:`wait` repeatedly until they see the
+desired state, while threads that modify the state call :meth:`notify` or
+:meth:`notifyAll` when they change the state in such a way that it could
+possibly be a desired state for one of the waiters. For example, the following
+code is a generic producer-consumer situation with unlimited buffer capacity::
+
+ # Consume one item
+ cv.acquire()
+ while not an_item_is_available():
+ cv.wait()
+ get_an_available_item()
+ cv.release()
+
+ # Produce one item
+ cv.acquire()
+ make_an_item_available()
+ cv.notify()
+ cv.release()
+
+To choose between :meth:`notify` and :meth:`notifyAll`, consider whether one
+state change can be interesting for only one or several waiting threads. E.g.
+in a typical producer-consumer situation, adding one item to the buffer only
+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.
+
+
+.. method:: Condition.acquire(*args)
+
+ Acquire the underlying lock. This method calls the corresponding method on the
+ underlying lock; the return value is whatever that method returns.
+
+
+.. method:: Condition.release()
+
+ Release the underlying lock. This method calls the corresponding method on the
+ underlying lock; there is no return value.
+
+
+.. method:: Condition.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.
+
+ This method releases the underlying lock, and then blocks until it is awakened
+ by a :meth:`notify` or :meth:`notifyAll` 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 *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).
+
+ 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.
+
+
+.. method:: Condition.notify()
+
+ Wake up a thread waiting on this condition, if any. 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.
+
+ 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.
+
+ 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.notifyAll()
+
+ 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:
+
+Semaphore Objects
+-----------------
+
+This is one of the oldest synchronization primitives in the history of computer
+science, invented by the early Dutch computer scientist Edsger W. Dijkstra (he
+used :meth:`P` and :meth:`V` instead of :meth:`acquire` and :meth:`release`).
+
+A semaphore manages an internal counter which is decremented by each
+:meth:`acquire` call and incremented by each :meth:`release` call. The counter
+can never go below zero; when :meth:`acquire` finds that it is zero, it blocks,
+waiting until some other thread calls :meth:`release`.
+
+
+.. class:: Semaphore([value])
+
+ The optional argument gives the initial *value* for the internal counter; it
+ defaults to ``1``. If the *value* given is less than 0, :exc:`ValueError` is
+ raised.
+
+
+.. 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.
+
+ 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()
+
+ 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:
+
+:class:`Semaphore` Example
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Semaphores are often used to guard resources with limited capacity, for example,
+a database server. In any situation where the size of the resource size is
+fixed, you should use a bounded semaphore. Before spawning any worker threads,
+your main thread would initialize the semaphore::
+
+ maxconnections = 5
+ ...
+ pool_sema = BoundedSemaphore(value=maxconnections)
+
+Once spawned, worker threads call the semaphore's acquire and release methods
+when they need to connect to the server::
+
+ pool_sema.acquire()
+ conn = connectdb()
+ ... use connection ...
+ conn.close()
+ pool_sema.release()
+
+The use of a bounded semaphore reduces the chance that a programming error which
+causes the semaphore to be released more than it's acquired will go undetected.
+
+
+.. _event-objects:
+
+Event Objects
+-------------
+
+This is one of the simplest mechanisms for communication between threads: one
+thread signals an event and other threads wait for it.
+
+An event object manages an internal flag that can be set to true with the
+:meth:`set` method and reset to false with the :meth:`clear` method. The
+:meth:`wait` method blocks until the flag is true.
+
+
+.. class:: Event()
+
+ The internal flag is initially false.
+
+
+.. method:: Event.isSet()
+
+ Return true if and only if the internal flag is true.
+
+
+.. method:: Event.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.clear()
+
+ 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:: 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).
+
+
+.. _thread-objects:
+
+Thread Objects
+--------------
+
+This class represents an activity that is run in a separate thread of control.
+There are two ways to specify the activity: by passing a callable object to the
+constructor, or by overriding the :meth:`run` method in a subclass. No other
+methods (except for the constructor) should be overridden in a subclass. In
+other words, *only* override the :meth:`__init__` and :meth:`run` methods of
+this class.
+
+Once a thread object is created, its activity must be started by calling the
+thread's :meth:`start` method. This invokes the :meth:`run` method in a
+separate thread of control.
+
+Once the thread's activity is started, the thread is considered 'alive'. It
+stops being alive when its :meth:`run` method terminates -- either normally, or
+by raising an unhandled exception. The :meth:`isAlive` method tests whether the
+thread is alive.
+
+Other threads can call a thread's :meth:`join` method. This blocks the calling
+thread until the thread whose :meth:`join` method is called is terminated.
+
+A thread has a name. The name can be passed to the constructor, set with the
+:meth:`setName` method, and retrieved with the :meth:`getName` method.
+
+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 with
+the :meth:`setDaemon` method and retrieved with the :meth:`isDaemon` method.
+
+There is a "main thread" object; this corresponds to the initial thread of
+control in the Python program. It is not a daemon thread.
+
+There is the possibility that "dummy thread objects" are created. These are
+thread objects corresponding to "alien threads", which are threads of control
+started outside the threading module, such as directly from C code. Dummy
+thread objects have limited functionality; they are always considered alive and
+daemonic, and cannot be :meth:`join`\ ed. They are never deleted, since it is
+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:
+
+ *group* should be ``None``; reserved for future extension when a
+ :class:`ThreadGroup` class is implemented.
+
+ *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.
+
+ *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.
+
+ This method will raise a :exc:`RuntimeException` if called more than once on the
+ same thread object.
+
+
+.. method:: Thread.run()
+
+ Method representing the thread's activity.
+
+ 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:: Thread.join([timeout])
+
+ 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 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:`isAlive` to decide whether a timeout happened.
+
+ When the *timeout* argument is not present or ``None``, the operation will block
+ until the thread terminates.
+
+ A thread can be :meth:`join`\ ed many times.
+
+ :meth:`join` may throw 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
+ same exception.
+
+
+.. method:: Thread.getName()
+
+ Return the thread's name.
+
+
+.. method:: Thread.setName(name)
+
+ Set the thread's name.
+
+ The name is 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:: Thread.isAlive()
+
+ 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.isDaemon()
+
+ Return the thread's daemon flag.
+
+
+.. method:: Thread.setDaemon(daemonic)
+
+ Set the thread's daemon flag to the Boolean value *daemonic*. This must be
+ called before :meth:`start` is called, otherwise :exc:`RuntimeError` is raised.
+
+ The initial value is inherited from the creating thread.
+
+ The entire Python program exits when no alive non-daemon threads are left.
+
+
+.. _timer-objects:
+
+Timer Objects
+-------------
+
+This class represents an action that should be run only after a certain amount
+of time has passed --- a timer. :class:`Timer` is a subclass of :class:`Thread`
+and as such also functions as an example of creating custom threads.
+
+Timers are started, as with threads, by calling their :meth:`start` method. The
+timer can be stopped (before its action has begun) by calling the :meth:`cancel`
+method. The interval the timer will wait before executing its action may not be
+exactly the same as the interval specified by the user.
+
+For example::
+
+ def hello():
+ print "hello, world"
+
+ t = Timer(30.0, hello)
+ t.start() # after 30 seconds, "hello, world" will be printed
+
+
+.. class:: Timer(interval, function, args=[], kwargs={})
+
+ Create a timer that will run *function* with arguments *args* and keyword
+ arguments *kwargs*, after *interval* seconds have passed.
+
+
+.. 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.
+
+
+.. _with-locks:
+
+Using locks, conditions, and semaphores in the :keyword:`with` statement
+------------------------------------------------------------------------
+
+All of the objects provided by this module that have :meth:`acquire` and
+:meth:`release` methods can be used as context managers for a :keyword:`with`
+statement. The :meth:`acquire` method will be called when the block is entered,
+and :meth:`release` will be called when the block is exited.
+
+Currently, :class:`Lock`, :class:`RLock`, :class:`Condition`,
+:class:`Semaphore`, and :class:`BoundedSemaphore` objects may be used as
+:keyword:`with` statement context managers. For example::
+
+ from __future__ import with_statement
+ import threading
+
+ some_rlock = threading.RLock()
+
+ with some_rlock:
+ print "some_rlock is locked while this executes"
+