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author | Guido van Rossum <guido@python.org> | 1999-04-13 04:20:48 (GMT) |
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committer | Guido van Rossum <guido@python.org> | 1999-04-13 04:20:48 (GMT) |
commit | ba3ed56a222f5d14b535c56035131b4a5906f2d5 (patch) | |
tree | 232cb0d8a229721958c2a974da9539f0ddc0b19f /Lib | |
parent | 7a1229991de8d1a275823acb7d7d2cf5be1cc776 (diff) | |
download | cpython-ba3ed56a222f5d14b535c56035131b4a5906f2d5.zip cpython-ba3ed56a222f5d14b535c56035131b4a5906f2d5.tar.gz cpython-ba3ed56a222f5d14b535c56035131b4a5906f2d5.tar.bz2 |
Removed; since long subsumed in Doc/lib/libthreading.tex
Diffstat (limited to 'Lib')
-rw-r--r-- | Lib/threading_api.py | 638 |
1 files changed, 0 insertions, 638 deletions
diff --git a/Lib/threading_api.py b/Lib/threading_api.py deleted file mode 100644 index ff97b8f..0000000 --- a/Lib/threading_api.py +++ /dev/null @@ -1,638 +0,0 @@ -"""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, daemonic): - """Set the thread's daemon flag (a Boolean). - - 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. - - """ |