New Java-style threading module. The doc strings are in a separate module.
diff --git a/Lib/threading.py b/Lib/threading.py
new file mode 100644
index 0000000..79319c1
--- /dev/null
+++ b/Lib/threading.py
@@ -0,0 +1,638 @@
+# threading.py:
+# Proposed new threading module, emulating a subset of Java's threading model
+
+import sys
+import time
+import thread
+import traceback
+import StringIO
+
+# Rename some stuff so "from threading import *" is safe
+
+_sys = sys
+del sys
+
+_time = time.time
+_sleep = time.sleep
+del time
+
+_start_new_thread = thread.start_new_thread
+_allocate_lock = thread.allocate_lock
+_get_ident = thread.get_ident
+del thread
+
+_print_exc = traceback.print_exc
+del traceback
+
+_StringIO = StringIO.StringIO
+del StringIO
+
+
+# Debug support (adapted from ihooks.py)
+
+_VERBOSE = 0
+
+if __debug__:
+
+ class _Verbose:
+
+ def __init__(self, verbose=None):
+ if verbose is None:
+ verbose = _VERBOSE
+ self.__verbose = verbose
+
+ def _note(self, format, *args):
+ if self.__verbose:
+ format = format % args
+ format = "%s: %s\n" % (
+ currentThread().getName(), format)
+ _sys.stderr.write(format)
+
+else:
+ # Disable this when using "python -O"
+ class _Verbose:
+ def __init__(self, verbose=None):
+ pass
+ def _note(self, *args):
+ pass
+
+
+# Synchronization classes
+
+Lock = _allocate_lock
+
+def RLock(*args, **kwargs):
+ return apply(_RLock, args, kwargs)
+
+class _RLock(_Verbose):
+
+ def __init__(self, verbose=None):
+ _Verbose.__init__(self, verbose)
+ self.__block = _allocate_lock()
+ self.__owner = None
+ self.__count = 0
+
+ def __repr__(self):
+ return "<%s(%s, %d)>" % (
+ self.__class__.__name__,
+ self.__owner and self.__owner.getName(),
+ self.__count)
+
+ def acquire(self, blocking=1):
+ me = currentThread()
+ if self.__owner is me:
+ self.__count = self.__count + 1
+ if __debug__:
+ self._note("%s.acquire(%s): recursive success", self, blocking)
+ return 1
+ rc = self.__block.acquire(blocking)
+ if rc:
+ self.__owner = me
+ self.__count = 1
+ if __debug__:
+ self._note("%s.acquire(%s): initial succes", self, blocking)
+ else:
+ if __debug__:
+ self._note("%s.acquire(%s): failure", self, blocking)
+ return rc
+
+ def release(self):
+ me = currentThread()
+ assert self.__owner is me, "release() of un-acquire()d lock"
+ self.__count = count = self.__count - 1
+ if not count:
+ self.__owner = None
+ self.__block.release()
+ if __debug__:
+ self._note("%s.release(): final release", self)
+ else:
+ if __debug__:
+ self._note("%s.release(): non-final release", self)
+
+ # Internal methods used by condition variables
+
+ def _acquire_restore(self, (count, owner)):
+ self.__block.acquire()
+ self.__count = count
+ self.__owner = owner
+ if __debug__:
+ self._note("%s._acquire_restore()", self)
+
+ def _release_save(self):
+ if __debug__:
+ self._note("%s._release_save()", self)
+ count = self.__count
+ self.__count = 0
+ owner = self.__owner
+ self.__owner = None
+ self.__block.release()
+ return (count, owner)
+
+ def _is_owned(self):
+ return self.__owner is currentThread()
+
+
+def Condition(*args, **kwargs):
+ return apply(_Condition, args, kwargs)
+
+class _Condition(_Verbose):
+
+ def __init__(self, lock=None, verbose=None):
+ _Verbose.__init__(self, verbose)
+ if lock is None:
+ lock = RLock()
+ self.__lock = lock
+ # Export the lock's acquire() and release() methods
+ self.acquire = lock.acquire
+ self.release = lock.release
+ # If the lock defines _release_save() and/or _acquire_restore(),
+ # these override the default implementations (which just call
+ # release() and acquire() on the lock). Ditto for _is_owned().
+ try:
+ self._release_save = lock._release_save
+ except AttributeError:
+ pass
+ try:
+ self._acquire_restore = lock._acquire_restore
+ except AttributeError:
+ pass
+ try:
+ self._is_owned = lock._is_owned
+ except AttributeError:
+ pass
+ self.__waiters = []
+
+ def __repr__(self):
+ return "<Condition(%s, %d)>" % (self.__lock, len(self.__waiters))
+
+ def _release_save(self):
+ self.__lock.release() # No state to save
+
+ def _acquire_restore(self, x):
+ self.__lock.acquire() # Ignore saved state
+
+ def _is_owned(self):
+ if self.__lock.acquire(0):
+ self.__lock.release()
+ return 0
+ else:
+ return 1
+
+ def wait(self, timeout=None):
+ me = currentThread()
+ assert self._is_owned(), "wait() of un-acquire()d lock"
+ waiter = _allocate_lock()
+ waiter.acquire()
+ self.__waiters.append(waiter)
+ saved_state = self._release_save()
+ if timeout is None:
+ waiter.acquire()
+ if __debug__:
+ self._note("%s.wait(): got it", self)
+ else:
+ endtime = _time() + timeout
+ delay = 0.000001 # 1 usec
+ while 1:
+ gotit = waiter.acquire(0)
+ if gotit or _time() >= endtime:
+ break
+ _sleep(delay)
+ if delay < 1.0:
+ delay = delay * 2.0
+ if not gotit:
+ if __debug__:
+ self._note("%s.wait(%s): timed out", self, timeout)
+ try:
+ self.__waiters.remove(waiter)
+ except ValueError:
+ pass
+ else:
+ if __debug__:
+ self._note("%s.wait(%s): got it", self, timeout)
+ self._acquire_restore(saved_state)
+
+ def notify(self, n=1):
+ me = currentThread()
+ assert self._is_owned(), "notify() of un-acquire()d lock"
+ __waiters = self.__waiters
+ waiters = __waiters[:n]
+ if not waiters:
+ if __debug__:
+ self._note("%s.notify(): no waiters", self)
+ return
+ self._note("%s.notify(): notifying %d waiter%s", self, n,
+ n!=1 and "s" or "")
+ for waiter in waiters:
+ waiter.release()
+ try:
+ __waiters.remove(waiter)
+ except ValueError:
+ pass
+
+ def notifyAll(self):
+ self.notify(len(self.__waiters))
+
+
+def Semaphore(*args, **kwargs):
+ return apply(_Semaphore, args, kwargs)
+
+class _Semaphore(_Verbose):
+
+ # After Tim Peters' semaphore class, but bnot quite the same (no maximum)
+
+ def __init__(self, value=1, verbose=None):
+ assert value >= 0, "Semaphore initial value must be >= 0"
+ _Verbose.__init__(self, verbose)
+ self.__cond = Condition(Lock())
+ self.__value = value
+
+ def acquire(self, blocking=1):
+ rc = 0
+ self.__cond.acquire()
+ while self.__value == 0:
+ if not blocking:
+ break
+ self.__cond.wait()
+ else:
+ self.__value = self.__value - 1
+ rc = 1
+ self.__cond.release()
+ return rc
+
+ def release(self):
+ self.__cond.acquire()
+ self.__value = self.__value + 1
+ self.__cond.notify()
+ self.__cond.release()
+
+
+def Event(*args, **kwargs):
+ return apply(_Event, args, kwargs)
+
+class _Event(_Verbose):
+
+ # After Tim Peters' event class (without is_posted())
+
+ def __init__(self, verbose=None):
+ _Verbose.__init__(self, verbose)
+ self.__cond = Condition(Lock())
+ self.__flag = 0
+
+ def isSet(self):
+ return self.__flag
+
+ def set(self):
+ self.__cond.acquire()
+ self.__flag = 1
+ self.__cond.notifyAll()
+ self.__cond.release()
+
+ def clear(self):
+ self.__cond.acquire()
+ self.__flag = 0
+ self.__cond.release()
+
+ def wait(self, timeout=None):
+ self.__cond.acquire()
+ if not self.__flag:
+ self.__cond.wait(timeout)
+ self.__cond.release()
+
+
+# Helper to generate new thread names
+_counter = 0
+def _newname(template="Thread-%d"):
+ global _counter
+ _counter = _counter + 1
+ return template % _counter
+
+# Active thread administration
+_active_limbo_lock = _allocate_lock()
+_active = {}
+_limbo = {}
+
+
+# Main class for threads
+
+class Thread(_Verbose):
+
+ __initialized = 0
+
+ def __init__(self, group=None, target=None, name=None,
+ args=(), kwargs={}, verbose=None):
+ assert group is None, "group argument must be None for now"
+ _Verbose.__init__(self, verbose)
+ self.__target = target
+ self.__name = str(name or _newname())
+ self.__args = args
+ self.__kwargs = kwargs
+ self.__daemonic = self._set_daemon()
+ self.__started = 0
+ self.__stopped = 0
+ self.__block = Condition(Lock())
+ self.__initialized = 1
+
+ def _set_daemon(self):
+ # Overridden in _MainThread and _DummyThread
+ return currentThread().isDaemon()
+
+ def __repr__(self):
+ assert self.__initialized, "Thread.__init__() was not called"
+ status = "initial"
+ if self.__started:
+ status = "started"
+ if self.__stopped:
+ status = "stopped"
+ if self.__daemonic:
+ status = status + " daemon"
+ return "<%s(%s, %s)>" % (self.__class__.__name__, self.__name, status)
+
+ def start(self):
+ assert self.__initialized, "Thread.__init__() not called"
+ assert not self.__started, "thread already started"
+ if __debug__:
+ self._note("%s.start(): starting thread", self)
+ _active_limbo_lock.acquire()
+ _limbo[self] = self
+ _active_limbo_lock.release()
+ _start_new_thread(self.__bootstrap, ())
+ self.__started = 1
+ _sleep(0.000001) # 1 usec, to let the thread run (Solaris hack)
+
+ def run(self):
+ if self.__target:
+ apply(self.__target, self.__args, self.__kwargs)
+
+ def __bootstrap(self):
+ try:
+ self.__started = 1
+ _active_limbo_lock.acquire()
+ _active[_get_ident()] = self
+ del _limbo[self]
+ _active_limbo_lock.release()
+ if __debug__:
+ self._note("%s.__bootstrap(): thread started", self)
+ try:
+ self.run()
+ except SystemExit:
+ if __debug__:
+ self._note("%s.__bootstrap(): raised SystemExit", self)
+ except:
+ if __debug__:
+ self._note("%s.__bootstrap(): unhandled exception", self)
+ s = _StringIO()
+ _print_exc(file=s)
+ _sys.stderr.write("Exception in thread %s:\n%s\n" %
+ (self.getName(), s.getvalue()))
+ else:
+ if __debug__:
+ self._note("%s.__bootstrap(): normal return", self)
+ finally:
+ self.__stop()
+ self.__delete()
+
+ def __stop(self):
+ self.__block.acquire()
+ self.__stopped = 1
+ self.__block.notifyAll()
+ self.__block.release()
+
+ def __delete(self):
+ _active_limbo_lock.acquire()
+ del _active[_get_ident()]
+ _active_limbo_lock.release()
+
+ def join(self, timeout=None):
+ assert self.__initialized, "Thread.__init__() not called"
+ assert self.__started, "cannot join thread before it is started"
+ assert self is not currentThread(), "cannot join current thread"
+ if __debug__:
+ if not self.__stopped:
+ self._note("%s.join(): waiting until thread stops", self)
+ self.__block.acquire()
+ if timeout is None:
+ while not self.__stopped:
+ self.__block.wait()
+ if __debug__:
+ self._note("%s.join(): thread stopped", self)
+ else:
+ deadline = time.time() + timeout
+ while not self.__stopped:
+ delay = deadline - time.time()
+ if delay <= 0:
+ if __debug__:
+ self._note("%s.join(): timed out", self)
+ break
+ self.__block.wait(delay)
+ else:
+ if __debug__:
+ self._note("%s.join(): thread stopped", self)
+ self.__block.release()
+
+ def getName(self):
+ assert self.__initialized, "Thread.__init__() not called"
+ return self.__name
+
+ def setName(self, name):
+ assert self.__initialized, "Thread.__init__() not called"
+ self.__name = str(name)
+
+ def isAlive(self):
+ assert self.__initialized, "Thread.__init__() not called"
+ return self.__started and not self.__stopped
+
+ def isDaemon(self):
+ assert self.__initialized, "Thread.__init__() not called"
+ return self.__daemonic
+
+ def setDaemon(self, daemonic):
+ assert self.__initialized, "Thread.__init__() not called"
+ assert not self.__started, "cannot set daemon status of active thread"
+ self.__daemonic = daemonic
+
+
+# Special thread class to represent the main thread
+# This is garbage collected through an exit handler
+
+class _MainThread(Thread):
+
+ def __init__(self):
+ Thread.__init__(self, name="MainThread")
+ self._Thread__started = 1
+ _active_limbo_lock.acquire()
+ _active[_get_ident()] = self
+ _active_limbo_lock.release()
+ try:
+ self.__oldexitfunc = _sys.exitfunc
+ except AttributeError:
+ self.__oldexitfunc = None
+ _sys.exitfunc = self.__exitfunc
+
+ def _set_daemon(self):
+ return 0
+
+ def __exitfunc(self):
+ self._Thread__stop()
+ t = _pickSomeNonDaemonThread()
+ if t:
+ if __debug__:
+ self._note("%s: waiting for other threads", self)
+ while t:
+ t.join()
+ t = _pickSomeNonDaemonThread()
+ if self.__oldexitfunc:
+ if __debug__:
+ self._note("%s: calling exit handler", self)
+ self.__oldexitfunc()
+ if __debug__:
+ self._note("%s: exiting", self)
+ self._Thread__delete()
+
+def _pickSomeNonDaemonThread():
+ for t in enumerate():
+ if not t.isDaemon() and t.isAlive():
+ return t
+ return None
+
+
+# Dummy thread class to represent threads not started here.
+# These aren't garbage collected when they die,
+# nor can they be waited for.
+# Their purpose is to return *something* from currentThread().
+# They are marked as daemon threads so we won't wait for them
+# when we exit (conform previous semantics).
+
+class _DummyThread(Thread):
+
+ def __init__(self):
+ Thread.__init__(self, name=_newname("Dummy-%d"))
+ self.__Thread_started = 1
+ _active_limbo_lock.acquire()
+ _active[_get_ident()] = self
+ _active_limbo_lock.release()
+
+ def _set_daemon(self):
+ return 1
+
+ def join(self):
+ assert 0, "cannot join a dummy thread"
+
+
+# Global API functions
+
+def currentThread():
+ try:
+ return _active[_get_ident()]
+ except KeyError:
+ print "currentThread(): no current thread for", _get_ident()
+ return _DummyThread()
+
+def activeCount():
+ _active_limbo_lock.acquire()
+ count = len(_active) + len(_limbo)
+ _active_limbo_lock.release()
+ return count
+
+def enumerate():
+ _active_limbo_lock.acquire()
+ active = _active.values() + _limbo.values()
+ _active_limbo_lock.release()
+ return active
+
+
+# Create the main thread object
+
+_MainThread()
+
+
+# Self-test code
+
+def _test():
+
+ import whrandom
+
+ class BoundedQueue(_Verbose):
+
+ def __init__(self, limit):
+ _Verbose.__init__(self)
+ self.mon = RLock()
+ self.rc = Condition(self.mon)
+ self.wc = Condition(self.mon)
+ self.limit = limit
+ self.queue = []
+
+ def put(self, item):
+ self.mon.acquire()
+ while len(self.queue) >= self.limit:
+ self._note("put(%s): queue full", item)
+ self.wc.wait()
+ self.queue.append(item)
+ self._note("put(%s): appended, length now %d",
+ item, len(self.queue))
+ self.rc.notify()
+ self.mon.release()
+
+ def get(self):
+ self.mon.acquire()
+ while not self.queue:
+ self._note("get(): queue empty")
+ self.rc.wait()
+ item = self.queue[0]
+ del self.queue[0]
+ self._note("get(): got %s, %d left", item, len(self.queue))
+ self.wc.notify()
+ self.mon.release()
+ return item
+
+ class ProducerThread(Thread):
+
+ def __init__(self, queue, quota):
+ Thread.__init__(self, name="Producer")
+ self.queue = queue
+ self.quota = quota
+
+ def run(self):
+ from whrandom import random
+ counter = 0
+ while counter < self.quota:
+ counter = counter + 1
+ self.queue.put("%s.%d" % (self.getName(), counter))
+ _sleep(random() * 0.00001)
+
+
+ class ConsumerThread(Thread):
+
+ def __init__(self, queue, count):
+ Thread.__init__(self, name="Consumer")
+ self.queue = queue
+ self.count = count
+
+ def run(self):
+ while self.count > 0:
+ item = self.queue.get()
+ print item
+ self.count = self.count - 1
+
+ import time
+
+ NP = 3
+ QL = 4
+ NI = 5
+
+ Q = BoundedQueue(QL)
+ P = []
+ for i in range(NP):
+ t = ProducerThread(Q, NI)
+ t.setName("Producer-%d" % (i+1))
+ P.append(t)
+ C = ConsumerThread(Q, NI*NP)
+ for t in P:
+ t.start()
+ _sleep(0.000001)
+ C.start()
+ for t in P:
+ t.join()
+ C.join()
+
+if __name__ == '__main__':
+ _test()
diff --git a/Lib/threading_api.py b/Lib/threading_api.py
new file mode 100644
index 0000000..285cee1
--- /dev/null
+++ b/Lib/threading_api.py
@@ -0,0 +1,638 @@
+"""Proposed new higher-level threading interfaces.
+
+This module is safe for use with 'from threading import *'. It
+defines the following objects:
+
+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.
+
+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.
+
+Condition()
+ 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.
+
+Semaphore()
+ A factory function that returns a new semaphore object. A
+ semaphore manages a counter representing the number of release()
+ calls minus the number of acquire() calls, plus an initial value.
+ The acquire() method blocks if necessary until it can return
+ without making the counter negative.
+
+Event()
+ A factory function that returns a new event object. An event
+ manages a flag that can be set to true with the set() method and
+ reset to false with the clear() method. The wait() method blocks
+ until the flag is true.
+
+Thread
+ A class that represents a thread of control -- subclassable.
+
+currentThread()
+ A function that returns the Thread object for the caller's thread.
+
+activeCount()
+ A function that returns the number of currently active threads.
+
+enumerate()
+ A function that returns a list of all currently active threads.
+
+Detailed interfaces for each of these are documented below in the form
+of pseudo class definitions. Note that the classes marked as ``do not
+subclass'' are actually implemented as factory functions; classes are
+shown here as a way to structure the documentation only.
+
+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 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 methods described below are executed atomically.
+
+"""
+
+
+class Lock:
+ """Primitive lock object.
+
+ *** DO NOT SUBCLASS THIS CLASS ***
+
+ 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 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, acquire() and release(). When the state is
+ unlocked, acquire() changes the state to locked and returns
+ immediately. When the state is locked, acquire() blocks until a
+ call to release() in another thread changes it to unlocked, then
+ the acquire() call resets it to locked and returns. The release()
+ method should only be called in the locked state; it changes the
+ state to unlocked and returns immediately. When more than one
+ thread is blocked in acquire() waiting for the state to turn to
+ unlocked, only one thread proceeds when a 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.
+
+ """
+
+ def acquire(self, 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. 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 argument would block, return false
+ immediately; otherwise, do the same thing as when called
+ without arguments, and return true.
+
+ """
+
+ def release(self):
+ """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.
+
+ """
+
+
+class RLock:
+ """Reentrant lock object.
+
+ *** DO NOT SUBCLASS THIS CLASS ***
+
+ 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 acquire() method; this
+ returns once the thread owns the lock. To unlock the lock, a
+ thread calls its release() method. acquire()/release() call pairs
+ may be nested; only the final release() (i.e. the release() of the
+ outermost pair) resets the lock to unlocked and allows another
+ thread blocked in acquire() to proceed.
+
+ """
+
+ def acquire(self, 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 argument would block, return false
+ immediately; otherwise, do the same thing as when called
+ without arguments, and return true.
+
+ """
+
+ def release(self):
+ """Release a lock.
+
+ Only call this method when the calling thread owns the lock.
+ Decrement 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.
+
+ Do not call this method when the lock is unlocked.
+
+ There is no return value.
+
+ """
+
+
+class Condition:
+ """Synchronized condition variable object.
+
+ *** DO NOT SUBCLASS THIS CLASS ***
+
+ 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 acquire() and release() methods that call
+ the corresponding methods of the associated lock.
+
+ It also has a wait() method, and notify() and notifyAll() methods.
+ These three must only be called when the calling thread has
+ acquired the lock.
+
+ The wait() method releases the lock, and then blocks until it is
+ awakened by a notifiy() or 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 notify() method wakes up one of the threads waiting for the
+ condition variable, if any are waiting. The notifyAll() method
+ wakes up all threads waiting for the condition variable.
+
+ Note: the notify() and notifyAll() methods don't release the
+ lock; this means that the thread or threads awakened will not
+ return from their wait() call immediately, but only when the
+ thread that called notify() or 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 wait()
+ repeatedly until they see the desired state, while threads that
+ modify the state call notify() or 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 notify() and 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.
+
+ """
+
+ def __init__(self, lock=None):
+ """Constructor.
+
+ If the lock argument is given and not None, it must be a Lock
+ or RLock object, and it is used as the underlying lock.
+ Otherwise, a new RLock object is created and used as the
+ underlying lock.
+
+ """
+
+ def acquire(self, *args):
+ """Acquire the underlying lock.
+
+ This method calls the corresponding method on the underlying
+ lock; the return value is whatever that method returns.
+
+ """
+
+ def release(self):
+ """Release the underlying lock.
+
+ This method calls the corresponding method on the underlying
+ lock; there is no return value.
+
+ """
+
+ def wait(self, timeout=None):
+ """Wait until notified or until a timeout occurs.
+
+ This must only be called when the calling thread has acquired
+ the lock.
+
+ This method releases the underlying lock, and then blocks
+ until it is awakened by a notify() or 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 RLock, it is not released using
+ its release() method, since this may not actually unlock the
+ lock when it was acquired() multiple times recursively.
+ Instead, an internal interface of the 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.
+
+ """
+
+ def notify(self):
+ """Wake up a thread waiting on this condition, if any.
+
+ This must only be called when the calling thread has acquired
+ the lock.
+
+ 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
+ wait() call until it can reacquire the lock. Since notify()
+ does not release the lock, its caller should.
+
+ """
+
+ def notifyAll(self):
+ """Wake up all threads waiting on this condition.
+
+ This method acts like notify(), but wakes up all waiting
+ threads instead of one.
+
+ """
+
+
+class Semaphore:
+ """Semaphore object.
+
+ 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 P() and V() instead of
+ acquire() and release()).
+
+ A semaphore manages an internal counter which is decremented by
+ each acquire() call and incremented by each release() call. The
+ counter can never go below zero; when acquire() finds that it is
+ zero, it blocks, waiting until some other thread calls release().
+
+ """
+
+ def __init__(self, value=1):
+ """Constructor.
+
+ The optional argument gives the initial value for the internal
+ counter; it defaults to 1.
+
+ """
+
+ def acquire(self, blocking=1):
+ """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 release() to make it larger than
+ zero. This is done with proper interlocking so that if
+ multiple acquire() calls are blocked, 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 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 argument would block, return false
+ immediately; otherwise, do the same thing as when called
+ without arguments, and return true.
+
+ """
+
+ def release(self):
+ """Release a semaphore.
+
+ Increment 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.
+
+ """
+
+
+class Event:
+ """Event object.
+
+ This is one of the simplest mechanisms for communication between
+ threads: one thread signals an event and another thread, or
+ threads, wait for it.
+
+ An event object manages an internal flag that can be set to true
+ with the set() method and reset to false with the clear() method.
+ The wait() method blocks until the flag is true.
+
+ """
+
+ def __init__(self):
+ """Constructor.
+
+ The internal flag is initially false.
+
+ """
+
+ def isSet(self):
+ """Return true iff the internal flag is true."""
+
+ def set(self):
+ """Set the internal flag to true.
+
+ All threads waiting for it to become true are awakened.
+
+ Threads that call wait() once the flag is true will not block
+ at all.
+
+ """
+
+ def clear(self):
+ """Reset the internal flag to false.
+
+ Subsequently, threads calling wait() will block until set() is
+ called to set the internal flag to true again.
+
+ """
+
+ def wait(self, timeout=None):
+ """Block until the internal flag is true.
+
+ If the internal flag is true on entry, return immediately.
+ Otherwise, block until another thread calls 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).
+
+ """
+
+
+class Thread:
+ """Thread class.
+
+ *** ONLY OVERRIDE THE __init__() AND run() METHODS OF THIS CLASS ***
+
+ 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
+ run() method in a subclass. No other methods (except for the
+ constructor) should be overridden in a subclass.
+
+ Once a thread object is created, its activity must be started by
+ calling the thread's start() method. This invokes the run()
+ method in a separate thread of control.
+
+ Once the thread's activity is started, the thread is considered
+ 'alive' and 'active' (these concepts are almost, but not quite
+ exactly, the same; their definition is intentionally somewhat
+ vague). It stops being alive and active when its run() method
+ terminates -- either normally, or by raising an unhandled
+ exception. The isAlive() method tests whether the thread is
+ alive.
+
+ Other threads can call a thread's join() method. This blocks the
+ calling thread until the thread whose join() method is called
+ is terminated.
+
+ A thread has a name. The name can be passed to the constructor,
+ set with the setName() method, and retrieved with the 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 setDaemon() method
+ and retrieved with the getDaemon() 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''. These are threads of control started outside the
+ threading module, e.g. directly from C code. Dummy thread objects
+ have limited functionality; they are always considered alive,
+ active, and daemonic, and cannot be join()ed. They are never
+ deleted, since it is impossible to detect the termination of alien
+ threads.
+
+ """
+
+ def __init__(self, group=None, target=None, name=None,
+ args=(), kwargs={}):
+ """Thread constructor.
+
+ This constructor should always be called with keyword
+ arguments. Arguments are:
+
+ group
+ Should be None; reserved for future extension when a
+ ThreadGroup class is implemented.
+
+ target
+ Callable object to be invoked by the run() method.
+ Defaults to None, meaning nothing is called.
+
+ name
+ The thread name. By default, a unique name is constructed
+ of the form ``Thread-N'' where N is a small decimal
+ number.
+
+ args
+ Argument tuple for the target invocation. Defaults to ().
+
+ kwargs
+ Keyword argument dictionary 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.
+
+ """
+
+ def start(self):
+ """Start the thread's activity.
+
+ This must be called at most once per thread object. It
+ arranges for the object's run() method to be invoked in a
+ separate thread of control.
+
+ """
+
+ def run(self):
+ """Method representing the thread's activity.
+
+ You may override this method in a subclass. The standard
+ run() method invokes the callable object passed as the
+ 'target' argument, if any, with sequential and keyword
+ arguments taken from the 'args' and 'kwargs' arguments,
+ respectively.
+
+ """
+
+ def join(self, timeout=None):
+ """Wait until the thread terminates.
+
+ This blocks the calling thread until the thread whose 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).
+
+ A thread can be join()ed many times.
+
+ A thread cannot join itself because this would cause a
+ deadlock.
+
+ It is an error to attempt to join() a thread before it has
+ been started.
+
+ """
+
+ def getName(self):
+ """Return the thread's name."""
+
+ def setName(self, 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.
+
+ """
+
+ def isAlive(self):
+ """Return whether the thread is alive.
+
+ Roughly, a thread is alive from the moment the start() method
+ returns until its run() method terminates.
+
+ """
+
+ def isDaemon(self):
+ """Return the thread's daemon flag."""
+
+ def setDaemon(self):
+ """Set the thread's daemon flag.
+
+ This must be called before start() is called.
+
+ The initial value is inherited from the creating thread.
+
+ The entire Python program exits when no active non-daemon
+ threads are left.
+
+ """
+
+
+# Module-level functions:
+
+
+def currentThread():
+ """Return the current Thread object.
+
+ This function returns the Thread object corresponding to the
+ caller's thread of control.
+
+ If the caller's thread of control was not created through the
+ threading module, a dummy thread object with limited functionality
+ is returned.
+
+ """
+
+
+def activeCount():
+ """Return the number of currently active Thread objects.
+
+ The returned count is equal to the length of the list returned by
+ enumerate().
+
+ """
+
+
+def enumerate():
+ """Return a list of all currently active Thread objects.
+
+ The list includes daemonic threads, dummy thread objects created
+ by currentThread(), and the main thread. It excludes terminated
+ threads and threads that have not yet been started.
+
+ """