Coverage for /pythoncovmergedfiles/medio/medio/usr/lib/python3.9/threading.py: 4%
684 statements
« prev ^ index » next coverage.py v7.3.2, created at 2023-10-20 07:00 +0000
1"""Thread module emulating a subset of Java's threading model."""
3import os as _os
4import sys as _sys
5import _thread
6import functools
8from time import monotonic as _time
9from _weakrefset import WeakSet
10from itertools import islice as _islice, count as _count
11try:
12 from _collections import deque as _deque
13except ImportError:
14 from collections import deque as _deque
16# Note regarding PEP 8 compliant names
17# This threading model was originally inspired by Java, and inherited
18# the convention of camelCase function and method names from that
19# language. Those original names are not in any imminent danger of
20# being deprecated (even for Py3k),so this module provides them as an
21# alias for the PEP 8 compliant names
22# Note that using the new PEP 8 compliant names facilitates substitution
23# with the multiprocessing module, which doesn't provide the old
24# Java inspired names.
26__all__ = ['get_ident', 'active_count', 'Condition', 'current_thread',
27 'enumerate', 'main_thread', 'TIMEOUT_MAX',
28 'Event', 'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Thread',
29 'Barrier', 'BrokenBarrierError', 'Timer', 'ThreadError',
30 'setprofile', 'settrace', 'local', 'stack_size',
31 'excepthook', 'ExceptHookArgs']
33# Rename some stuff so "from threading import *" is safe
34_start_new_thread = _thread.start_new_thread
35_allocate_lock = _thread.allocate_lock
36_set_sentinel = _thread._set_sentinel
37get_ident = _thread.get_ident
38try:
39 get_native_id = _thread.get_native_id
40 _HAVE_THREAD_NATIVE_ID = True
41 __all__.append('get_native_id')
42except AttributeError:
43 _HAVE_THREAD_NATIVE_ID = False
44ThreadError = _thread.error
45try:
46 _CRLock = _thread.RLock
47except AttributeError:
48 _CRLock = None
49TIMEOUT_MAX = _thread.TIMEOUT_MAX
50del _thread
53# Support for profile and trace hooks
55_profile_hook = None
56_trace_hook = None
58def setprofile(func):
59 """Set a profile function for all threads started from the threading module.
61 The func will be passed to sys.setprofile() for each thread, before its
62 run() method is called.
64 """
65 global _profile_hook
66 _profile_hook = func
68def settrace(func):
69 """Set a trace function for all threads started from the threading module.
71 The func will be passed to sys.settrace() for each thread, before its run()
72 method is called.
74 """
75 global _trace_hook
76 _trace_hook = func
78# Synchronization classes
80Lock = _allocate_lock
82def RLock(*args, **kwargs):
83 """Factory function that returns a new reentrant lock.
85 A reentrant lock must be released by the thread that acquired it. Once a
86 thread has acquired a reentrant lock, the same thread may acquire it again
87 without blocking; the thread must release it once for each time it has
88 acquired it.
90 """
91 if _CRLock is None:
92 return _PyRLock(*args, **kwargs)
93 return _CRLock(*args, **kwargs)
95class _RLock:
96 """This class implements reentrant lock objects.
98 A reentrant lock must be released by the thread that acquired it. Once a
99 thread has acquired a reentrant lock, the same thread may acquire it
100 again without blocking; the thread must release it once for each time it
101 has acquired it.
103 """
105 def __init__(self):
106 self._block = _allocate_lock()
107 self._owner = None
108 self._count = 0
110 def __repr__(self):
111 owner = self._owner
112 try:
113 owner = _active[owner].name
114 except KeyError:
115 pass
116 return "<%s %s.%s object owner=%r count=%d at %s>" % (
117 "locked" if self._block.locked() else "unlocked",
118 self.__class__.__module__,
119 self.__class__.__qualname__,
120 owner,
121 self._count,
122 hex(id(self))
123 )
125 def _at_fork_reinit(self):
126 self._block._at_fork_reinit()
127 self._owner = None
128 self._count = 0
130 def acquire(self, blocking=True, timeout=-1):
131 """Acquire a lock, blocking or non-blocking.
133 When invoked without arguments: if this thread already owns the lock,
134 increment the recursion level by one, and return immediately. Otherwise,
135 if another thread owns the lock, block until the lock is unlocked. Once
136 the lock is unlocked (not owned by any thread), then grab ownership, set
137 the recursion level to one, and return. If more than one thread is
138 blocked waiting until the lock is unlocked, only one at a time will be
139 able to grab ownership of the lock. There is no return value in this
140 case.
142 When invoked with the blocking argument set to true, do the same thing
143 as when called without arguments, and return true.
145 When invoked with the blocking argument set to false, do not block. If a
146 call without an argument would block, return false immediately;
147 otherwise, do the same thing as when called without arguments, and
148 return true.
150 When invoked with the floating-point timeout argument set to a positive
151 value, block for at most the number of seconds specified by timeout
152 and as long as the lock cannot be acquired. Return true if the lock has
153 been acquired, false if the timeout has elapsed.
155 """
156 me = get_ident()
157 if self._owner == me:
158 self._count += 1
159 return 1
160 rc = self._block.acquire(blocking, timeout)
161 if rc:
162 self._owner = me
163 self._count = 1
164 return rc
166 __enter__ = acquire
168 def release(self):
169 """Release a lock, decrementing the recursion level.
171 If after the decrement it is zero, reset the lock to unlocked (not owned
172 by any thread), and if any other threads are blocked waiting for the
173 lock to become unlocked, allow exactly one of them to proceed. If after
174 the decrement the recursion level is still nonzero, the lock remains
175 locked and owned by the calling thread.
177 Only call this method when the calling thread owns the lock. A
178 RuntimeError is raised if this method is called when the lock is
179 unlocked.
181 There is no return value.
183 """
184 if self._owner != get_ident():
185 raise RuntimeError("cannot release un-acquired lock")
186 self._count = count = self._count - 1
187 if not count:
188 self._owner = None
189 self._block.release()
191 def __exit__(self, t, v, tb):
192 self.release()
194 # Internal methods used by condition variables
196 def _acquire_restore(self, state):
197 self._block.acquire()
198 self._count, self._owner = state
200 def _release_save(self):
201 if self._count == 0:
202 raise RuntimeError("cannot release un-acquired lock")
203 count = self._count
204 self._count = 0
205 owner = self._owner
206 self._owner = None
207 self._block.release()
208 return (count, owner)
210 def _is_owned(self):
211 return self._owner == get_ident()
213_PyRLock = _RLock
216class Condition:
217 """Class that implements a condition variable.
219 A condition variable allows one or more threads to wait until they are
220 notified by another thread.
222 If the lock argument is given and not None, it must be a Lock or RLock
223 object, and it is used as the underlying lock. Otherwise, a new RLock object
224 is created and used as the underlying lock.
226 """
228 def __init__(self, lock=None):
229 if lock is None:
230 lock = RLock()
231 self._lock = lock
232 # Export the lock's acquire() and release() methods
233 self.acquire = lock.acquire
234 self.release = lock.release
235 # If the lock defines _release_save() and/or _acquire_restore(),
236 # these override the default implementations (which just call
237 # release() and acquire() on the lock). Ditto for _is_owned().
238 try:
239 self._release_save = lock._release_save
240 except AttributeError:
241 pass
242 try:
243 self._acquire_restore = lock._acquire_restore
244 except AttributeError:
245 pass
246 try:
247 self._is_owned = lock._is_owned
248 except AttributeError:
249 pass
250 self._waiters = _deque()
252 def _at_fork_reinit(self):
253 self._lock._at_fork_reinit()
254 self._waiters.clear()
256 def __enter__(self):
257 return self._lock.__enter__()
259 def __exit__(self, *args):
260 return self._lock.__exit__(*args)
262 def __repr__(self):
263 return "<Condition(%s, %d)>" % (self._lock, len(self._waiters))
265 def _release_save(self):
266 self._lock.release() # No state to save
268 def _acquire_restore(self, x):
269 self._lock.acquire() # Ignore saved state
271 def _is_owned(self):
272 # Return True if lock is owned by current_thread.
273 # This method is called only if _lock doesn't have _is_owned().
274 if self._lock.acquire(False):
275 self._lock.release()
276 return False
277 else:
278 return True
280 def wait(self, timeout=None):
281 """Wait until notified or until a timeout occurs.
283 If the calling thread has not acquired the lock when this method is
284 called, a RuntimeError is raised.
286 This method releases the underlying lock, and then blocks until it is
287 awakened by a notify() or notify_all() call for the same condition
288 variable in another thread, or until the optional timeout occurs. Once
289 awakened or timed out, it re-acquires the lock and returns.
291 When the timeout argument is present and not None, it should be a
292 floating point number specifying a timeout for the operation in seconds
293 (or fractions thereof).
295 When the underlying lock is an RLock, it is not released using its
296 release() method, since this may not actually unlock the lock when it
297 was acquired multiple times recursively. Instead, an internal interface
298 of the RLock class is used, which really unlocks it even when it has
299 been recursively acquired several times. Another internal interface is
300 then used to restore the recursion level when the lock is reacquired.
302 """
303 if not self._is_owned():
304 raise RuntimeError("cannot wait on un-acquired lock")
305 waiter = _allocate_lock()
306 waiter.acquire()
307 self._waiters.append(waiter)
308 saved_state = self._release_save()
309 gotit = False
310 try: # restore state no matter what (e.g., KeyboardInterrupt)
311 if timeout is None:
312 waiter.acquire()
313 gotit = True
314 else:
315 if timeout > 0:
316 gotit = waiter.acquire(True, timeout)
317 else:
318 gotit = waiter.acquire(False)
319 return gotit
320 finally:
321 self._acquire_restore(saved_state)
322 if not gotit:
323 try:
324 self._waiters.remove(waiter)
325 except ValueError:
326 pass
328 def wait_for(self, predicate, timeout=None):
329 """Wait until a condition evaluates to True.
331 predicate should be a callable which result will be interpreted as a
332 boolean value. A timeout may be provided giving the maximum time to
333 wait.
335 """
336 endtime = None
337 waittime = timeout
338 result = predicate()
339 while not result:
340 if waittime is not None:
341 if endtime is None:
342 endtime = _time() + waittime
343 else:
344 waittime = endtime - _time()
345 if waittime <= 0:
346 break
347 self.wait(waittime)
348 result = predicate()
349 return result
351 def notify(self, n=1):
352 """Wake up one or more threads waiting on this condition, if any.
354 If the calling thread has not acquired the lock when this method is
355 called, a RuntimeError is raised.
357 This method wakes up at most n of the threads waiting for the condition
358 variable; it is a no-op if no threads are waiting.
360 """
361 if not self._is_owned():
362 raise RuntimeError("cannot notify on un-acquired lock")
363 all_waiters = self._waiters
364 waiters_to_notify = _deque(_islice(all_waiters, n))
365 if not waiters_to_notify:
366 return
367 for waiter in waiters_to_notify:
368 waiter.release()
369 try:
370 all_waiters.remove(waiter)
371 except ValueError:
372 pass
374 def notify_all(self):
375 """Wake up all threads waiting on this condition.
377 If the calling thread has not acquired the lock when this method
378 is called, a RuntimeError is raised.
380 """
381 self.notify(len(self._waiters))
383 notifyAll = notify_all
386class Semaphore:
387 """This class implements semaphore objects.
389 Semaphores manage a counter representing the number of release() calls minus
390 the number of acquire() calls, plus an initial value. The acquire() method
391 blocks if necessary until it can return without making the counter
392 negative. If not given, value defaults to 1.
394 """
396 # After Tim Peters' semaphore class, but not quite the same (no maximum)
398 def __init__(self, value=1):
399 if value < 0:
400 raise ValueError("semaphore initial value must be >= 0")
401 self._cond = Condition(Lock())
402 self._value = value
404 def acquire(self, blocking=True, timeout=None):
405 """Acquire a semaphore, decrementing the internal counter by one.
407 When invoked without arguments: if the internal counter is larger than
408 zero on entry, decrement it by one and return immediately. If it is zero
409 on entry, block, waiting until some other thread has called release() to
410 make it larger than zero. This is done with proper interlocking so that
411 if multiple acquire() calls are blocked, release() will wake exactly one
412 of them up. The implementation may pick one at random, so the order in
413 which blocked threads are awakened should not be relied on. There is no
414 return value in this case.
416 When invoked with blocking set to true, do the same thing as when called
417 without arguments, and return true.
419 When invoked with blocking set to false, do not block. If a call without
420 an argument would block, return false immediately; otherwise, do the
421 same thing as when called without arguments, and return true.
423 When invoked with a timeout other than None, it will block for at
424 most timeout seconds. If acquire does not complete successfully in
425 that interval, return false. Return true otherwise.
427 """
428 if not blocking and timeout is not None:
429 raise ValueError("can't specify timeout for non-blocking acquire")
430 rc = False
431 endtime = None
432 with self._cond:
433 while self._value == 0:
434 if not blocking:
435 break
436 if timeout is not None:
437 if endtime is None:
438 endtime = _time() + timeout
439 else:
440 timeout = endtime - _time()
441 if timeout <= 0:
442 break
443 self._cond.wait(timeout)
444 else:
445 self._value -= 1
446 rc = True
447 return rc
449 __enter__ = acquire
451 def release(self, n=1):
452 """Release a semaphore, incrementing the internal counter by one or more.
454 When the counter is zero on entry and another thread is waiting for it
455 to become larger than zero again, wake up that thread.
457 """
458 if n < 1:
459 raise ValueError('n must be one or more')
460 with self._cond:
461 self._value += n
462 for i in range(n):
463 self._cond.notify()
465 def __exit__(self, t, v, tb):
466 self.release()
469class BoundedSemaphore(Semaphore):
470 """Implements a bounded semaphore.
472 A bounded semaphore checks to make sure its current value doesn't exceed its
473 initial value. If it does, ValueError is raised. In most situations
474 semaphores are used to guard resources with limited capacity.
476 If the semaphore is released too many times it's a sign of a bug. If not
477 given, value defaults to 1.
479 Like regular semaphores, bounded semaphores manage a counter representing
480 the number of release() calls minus the number of acquire() calls, plus an
481 initial value. The acquire() method blocks if necessary until it can return
482 without making the counter negative. If not given, value defaults to 1.
484 """
486 def __init__(self, value=1):
487 Semaphore.__init__(self, value)
488 self._initial_value = value
490 def release(self, n=1):
491 """Release a semaphore, incrementing the internal counter by one or more.
493 When the counter is zero on entry and another thread is waiting for it
494 to become larger than zero again, wake up that thread.
496 If the number of releases exceeds the number of acquires,
497 raise a ValueError.
499 """
500 if n < 1:
501 raise ValueError('n must be one or more')
502 with self._cond:
503 if self._value + n > self._initial_value:
504 raise ValueError("Semaphore released too many times")
505 self._value += n
506 for i in range(n):
507 self._cond.notify()
510class Event:
511 """Class implementing event objects.
513 Events manage a flag that can be set to true with the set() method and reset
514 to false with the clear() method. The wait() method blocks until the flag is
515 true. The flag is initially false.
517 """
519 # After Tim Peters' event class (without is_posted())
521 def __init__(self):
522 self._cond = Condition(Lock())
523 self._flag = False
525 def _at_fork_reinit(self):
526 # Private method called by Thread._reset_internal_locks()
527 self._cond._at_fork_reinit()
529 def is_set(self):
530 """Return true if and only if the internal flag is true."""
531 return self._flag
533 isSet = is_set
535 def set(self):
536 """Set the internal flag to true.
538 All threads waiting for it to become true are awakened. Threads
539 that call wait() once the flag is true will not block at all.
541 """
542 with self._cond:
543 self._flag = True
544 self._cond.notify_all()
546 def clear(self):
547 """Reset the internal flag to false.
549 Subsequently, threads calling wait() will block until set() is called to
550 set the internal flag to true again.
552 """
553 with self._cond:
554 self._flag = False
556 def wait(self, timeout=None):
557 """Block until the internal flag is true.
559 If the internal flag is true on entry, return immediately. Otherwise,
560 block until another thread calls set() to set the flag to true, or until
561 the optional timeout occurs.
563 When the timeout argument is present and not None, it should be a
564 floating point number specifying a timeout for the operation in seconds
565 (or fractions thereof).
567 This method returns the internal flag on exit, so it will always return
568 True except if a timeout is given and the operation times out.
570 """
571 with self._cond:
572 signaled = self._flag
573 if not signaled:
574 signaled = self._cond.wait(timeout)
575 return signaled
578# A barrier class. Inspired in part by the pthread_barrier_* api and
579# the CyclicBarrier class from Java. See
580# http://sourceware.org/pthreads-win32/manual/pthread_barrier_init.html and
581# http://java.sun.com/j2se/1.5.0/docs/api/java/util/concurrent/
582# CyclicBarrier.html
583# for information.
584# We maintain two main states, 'filling' and 'draining' enabling the barrier
585# to be cyclic. Threads are not allowed into it until it has fully drained
586# since the previous cycle. In addition, a 'resetting' state exists which is
587# similar to 'draining' except that threads leave with a BrokenBarrierError,
588# and a 'broken' state in which all threads get the exception.
589class Barrier:
590 """Implements a Barrier.
592 Useful for synchronizing a fixed number of threads at known synchronization
593 points. Threads block on 'wait()' and are simultaneously awoken once they
594 have all made that call.
596 """
598 def __init__(self, parties, action=None, timeout=None):
599 """Create a barrier, initialised to 'parties' threads.
601 'action' is a callable which, when supplied, will be called by one of
602 the threads after they have all entered the barrier and just prior to
603 releasing them all. If a 'timeout' is provided, it is used as the
604 default for all subsequent 'wait()' calls.
606 """
607 self._cond = Condition(Lock())
608 self._action = action
609 self._timeout = timeout
610 self._parties = parties
611 self._state = 0 #0 filling, 1, draining, -1 resetting, -2 broken
612 self._count = 0
614 def wait(self, timeout=None):
615 """Wait for the barrier.
617 When the specified number of threads have started waiting, they are all
618 simultaneously awoken. If an 'action' was provided for the barrier, one
619 of the threads will have executed that callback prior to returning.
620 Returns an individual index number from 0 to 'parties-1'.
622 """
623 if timeout is None:
624 timeout = self._timeout
625 with self._cond:
626 self._enter() # Block while the barrier drains.
627 index = self._count
628 self._count += 1
629 try:
630 if index + 1 == self._parties:
631 # We release the barrier
632 self._release()
633 else:
634 # We wait until someone releases us
635 self._wait(timeout)
636 return index
637 finally:
638 self._count -= 1
639 # Wake up any threads waiting for barrier to drain.
640 self._exit()
642 # Block until the barrier is ready for us, or raise an exception
643 # if it is broken.
644 def _enter(self):
645 while self._state in (-1, 1):
646 # It is draining or resetting, wait until done
647 self._cond.wait()
648 #see if the barrier is in a broken state
649 if self._state < 0:
650 raise BrokenBarrierError
651 assert self._state == 0
653 # Optionally run the 'action' and release the threads waiting
654 # in the barrier.
655 def _release(self):
656 try:
657 if self._action:
658 self._action()
659 # enter draining state
660 self._state = 1
661 self._cond.notify_all()
662 except:
663 #an exception during the _action handler. Break and reraise
664 self._break()
665 raise
667 # Wait in the barrier until we are released. Raise an exception
668 # if the barrier is reset or broken.
669 def _wait(self, timeout):
670 if not self._cond.wait_for(lambda : self._state != 0, timeout):
671 #timed out. Break the barrier
672 self._break()
673 raise BrokenBarrierError
674 if self._state < 0:
675 raise BrokenBarrierError
676 assert self._state == 1
678 # If we are the last thread to exit the barrier, signal any threads
679 # waiting for the barrier to drain.
680 def _exit(self):
681 if self._count == 0:
682 if self._state in (-1, 1):
683 #resetting or draining
684 self._state = 0
685 self._cond.notify_all()
687 def reset(self):
688 """Reset the barrier to the initial state.
690 Any threads currently waiting will get the BrokenBarrier exception
691 raised.
693 """
694 with self._cond:
695 if self._count > 0:
696 if self._state == 0:
697 #reset the barrier, waking up threads
698 self._state = -1
699 elif self._state == -2:
700 #was broken, set it to reset state
701 #which clears when the last thread exits
702 self._state = -1
703 else:
704 self._state = 0
705 self._cond.notify_all()
707 def abort(self):
708 """Place the barrier into a 'broken' state.
710 Useful in case of error. Any currently waiting threads and threads
711 attempting to 'wait()' will have BrokenBarrierError raised.
713 """
714 with self._cond:
715 self._break()
717 def _break(self):
718 # An internal error was detected. The barrier is set to
719 # a broken state all parties awakened.
720 self._state = -2
721 self._cond.notify_all()
723 @property
724 def parties(self):
725 """Return the number of threads required to trip the barrier."""
726 return self._parties
728 @property
729 def n_waiting(self):
730 """Return the number of threads currently waiting at the barrier."""
731 # We don't need synchronization here since this is an ephemeral result
732 # anyway. It returns the correct value in the steady state.
733 if self._state == 0:
734 return self._count
735 return 0
737 @property
738 def broken(self):
739 """Return True if the barrier is in a broken state."""
740 return self._state == -2
742# exception raised by the Barrier class
743class BrokenBarrierError(RuntimeError):
744 pass
747# Helper to generate new thread names
748_counter = _count().__next__
749_counter() # Consume 0 so first non-main thread has id 1.
750def _newname(template="Thread-%d"):
751 return template % _counter()
753# Active thread administration
754_active_limbo_lock = _allocate_lock()
755_active = {} # maps thread id to Thread object
756_limbo = {}
757_dangling = WeakSet()
758# Set of Thread._tstate_lock locks of non-daemon threads used by _shutdown()
759# to wait until all Python thread states get deleted:
760# see Thread._set_tstate_lock().
761_shutdown_locks_lock = _allocate_lock()
762_shutdown_locks = set()
764# Main class for threads
766class Thread:
767 """A class that represents a thread of control.
769 This class can be safely subclassed in a limited fashion. There are two ways
770 to specify the activity: by passing a callable object to the constructor, or
771 by overriding the run() method in a subclass.
773 """
775 _initialized = False
777 def __init__(self, group=None, target=None, name=None,
778 args=(), kwargs=None, *, daemon=None):
779 """This constructor should always be called with keyword arguments. Arguments are:
781 *group* should be None; reserved for future extension when a ThreadGroup
782 class is implemented.
784 *target* is the callable object to be invoked by the run()
785 method. Defaults to None, meaning nothing is called.
787 *name* is the thread name. By default, a unique name is constructed of
788 the form "Thread-N" where N is a small decimal number.
790 *args* is the argument tuple for the target invocation. Defaults to ().
792 *kwargs* is a dictionary of keyword arguments for the target
793 invocation. Defaults to {}.
795 If a subclass overrides the constructor, it must make sure to invoke
796 the base class constructor (Thread.__init__()) before doing anything
797 else to the thread.
799 """
800 assert group is None, "group argument must be None for now"
801 if kwargs is None:
802 kwargs = {}
803 self._target = target
804 self._name = str(name or _newname())
805 self._args = args
806 self._kwargs = kwargs
807 if daemon is not None:
808 self._daemonic = daemon
809 else:
810 self._daemonic = current_thread().daemon
811 self._ident = None
812 if _HAVE_THREAD_NATIVE_ID:
813 self._native_id = None
814 self._tstate_lock = None
815 self._started = Event()
816 self._is_stopped = False
817 self._initialized = True
818 # Copy of sys.stderr used by self._invoke_excepthook()
819 self._stderr = _sys.stderr
820 self._invoke_excepthook = _make_invoke_excepthook()
821 # For debugging and _after_fork()
822 _dangling.add(self)
824 def _reset_internal_locks(self, is_alive):
825 # private! Called by _after_fork() to reset our internal locks as
826 # they may be in an invalid state leading to a deadlock or crash.
827 self._started._at_fork_reinit()
828 if is_alive:
829 # bpo-42350: If the fork happens when the thread is already stopped
830 # (ex: after threading._shutdown() has been called), _tstate_lock
831 # is None. Do nothing in this case.
832 if self._tstate_lock is not None:
833 self._tstate_lock._at_fork_reinit()
834 self._tstate_lock.acquire()
835 else:
836 # The thread isn't alive after fork: it doesn't have a tstate
837 # anymore.
838 self._is_stopped = True
839 self._tstate_lock = None
841 def __repr__(self):
842 assert self._initialized, "Thread.__init__() was not called"
843 status = "initial"
844 if self._started.is_set():
845 status = "started"
846 self.is_alive() # easy way to get ._is_stopped set when appropriate
847 if self._is_stopped:
848 status = "stopped"
849 if self._daemonic:
850 status += " daemon"
851 if self._ident is not None:
852 status += " %s" % self._ident
853 return "<%s(%s, %s)>" % (self.__class__.__name__, self._name, status)
855 def start(self):
856 """Start the thread's activity.
858 It must be called at most once per thread object. It arranges for the
859 object's run() method to be invoked in a separate thread of control.
861 This method will raise a RuntimeError if called more than once on the
862 same thread object.
864 """
865 if not self._initialized:
866 raise RuntimeError("thread.__init__() not called")
868 if self._started.is_set():
869 raise RuntimeError("threads can only be started once")
871 with _active_limbo_lock:
872 _limbo[self] = self
873 try:
874 _start_new_thread(self._bootstrap, ())
875 except Exception:
876 with _active_limbo_lock:
877 del _limbo[self]
878 raise
879 self._started.wait()
881 def run(self):
882 """Method representing the thread's activity.
884 You may override this method in a subclass. The standard run() method
885 invokes the callable object passed to the object's constructor as the
886 target argument, if any, with sequential and keyword arguments taken
887 from the args and kwargs arguments, respectively.
889 """
890 try:
891 if self._target:
892 self._target(*self._args, **self._kwargs)
893 finally:
894 # Avoid a refcycle if the thread is running a function with
895 # an argument that has a member that points to the thread.
896 del self._target, self._args, self._kwargs
898 def _bootstrap(self):
899 # Wrapper around the real bootstrap code that ignores
900 # exceptions during interpreter cleanup. Those typically
901 # happen when a daemon thread wakes up at an unfortunate
902 # moment, finds the world around it destroyed, and raises some
903 # random exception *** while trying to report the exception in
904 # _bootstrap_inner() below ***. Those random exceptions
905 # don't help anybody, and they confuse users, so we suppress
906 # them. We suppress them only when it appears that the world
907 # indeed has already been destroyed, so that exceptions in
908 # _bootstrap_inner() during normal business hours are properly
909 # reported. Also, we only suppress them for daemonic threads;
910 # if a non-daemonic encounters this, something else is wrong.
911 try:
912 self._bootstrap_inner()
913 except:
914 if self._daemonic and _sys is None:
915 return
916 raise
918 def _set_ident(self):
919 self._ident = get_ident()
921 if _HAVE_THREAD_NATIVE_ID:
922 def _set_native_id(self):
923 self._native_id = get_native_id()
925 def _set_tstate_lock(self):
926 """
927 Set a lock object which will be released by the interpreter when
928 the underlying thread state (see pystate.h) gets deleted.
929 """
930 self._tstate_lock = _set_sentinel()
931 self._tstate_lock.acquire()
933 if not self.daemon:
934 with _shutdown_locks_lock:
935 _shutdown_locks.add(self._tstate_lock)
937 def _bootstrap_inner(self):
938 try:
939 self._set_ident()
940 self._set_tstate_lock()
941 if _HAVE_THREAD_NATIVE_ID:
942 self._set_native_id()
943 self._started.set()
944 with _active_limbo_lock:
945 _active[self._ident] = self
946 del _limbo[self]
948 if _trace_hook:
949 _sys.settrace(_trace_hook)
950 if _profile_hook:
951 _sys.setprofile(_profile_hook)
953 try:
954 self.run()
955 except:
956 self._invoke_excepthook(self)
957 finally:
958 with _active_limbo_lock:
959 try:
960 # We don't call self._delete() because it also
961 # grabs _active_limbo_lock.
962 del _active[get_ident()]
963 except:
964 pass
966 def _stop(self):
967 # After calling ._stop(), .is_alive() returns False and .join() returns
968 # immediately. ._tstate_lock must be released before calling ._stop().
969 #
970 # Normal case: C code at the end of the thread's life
971 # (release_sentinel in _threadmodule.c) releases ._tstate_lock, and
972 # that's detected by our ._wait_for_tstate_lock(), called by .join()
973 # and .is_alive(). Any number of threads _may_ call ._stop()
974 # simultaneously (for example, if multiple threads are blocked in
975 # .join() calls), and they're not serialized. That's harmless -
976 # they'll just make redundant rebindings of ._is_stopped and
977 # ._tstate_lock. Obscure: we rebind ._tstate_lock last so that the
978 # "assert self._is_stopped" in ._wait_for_tstate_lock() always works
979 # (the assert is executed only if ._tstate_lock is None).
980 #
981 # Special case: _main_thread releases ._tstate_lock via this
982 # module's _shutdown() function.
983 lock = self._tstate_lock
984 if lock is not None:
985 assert not lock.locked()
986 self._is_stopped = True
987 self._tstate_lock = None
988 if not self.daemon:
989 with _shutdown_locks_lock:
990 _shutdown_locks.discard(lock)
992 def _delete(self):
993 "Remove current thread from the dict of currently running threads."
994 with _active_limbo_lock:
995 del _active[get_ident()]
996 # There must not be any python code between the previous line
997 # and after the lock is released. Otherwise a tracing function
998 # could try to acquire the lock again in the same thread, (in
999 # current_thread()), and would block.
1001 def join(self, timeout=None):
1002 """Wait until the thread terminates.
1004 This blocks the calling thread until the thread whose join() method is
1005 called terminates -- either normally or through an unhandled exception
1006 or until the optional timeout occurs.
1008 When the timeout argument is present and not None, it should be a
1009 floating point number specifying a timeout for the operation in seconds
1010 (or fractions thereof). As join() always returns None, you must call
1011 is_alive() after join() to decide whether a timeout happened -- if the
1012 thread is still alive, the join() call timed out.
1014 When the timeout argument is not present or None, the operation will
1015 block until the thread terminates.
1017 A thread can be join()ed many times.
1019 join() raises a RuntimeError if an attempt is made to join the current
1020 thread as that would cause a deadlock. It is also an error to join() a
1021 thread before it has been started and attempts to do so raises the same
1022 exception.
1024 """
1025 if not self._initialized:
1026 raise RuntimeError("Thread.__init__() not called")
1027 if not self._started.is_set():
1028 raise RuntimeError("cannot join thread before it is started")
1029 if self is current_thread():
1030 raise RuntimeError("cannot join current thread")
1032 if timeout is None:
1033 self._wait_for_tstate_lock()
1034 else:
1035 # the behavior of a negative timeout isn't documented, but
1036 # historically .join(timeout=x) for x<0 has acted as if timeout=0
1037 self._wait_for_tstate_lock(timeout=max(timeout, 0))
1039 def _wait_for_tstate_lock(self, block=True, timeout=-1):
1040 # Issue #18808: wait for the thread state to be gone.
1041 # At the end of the thread's life, after all knowledge of the thread
1042 # is removed from C data structures, C code releases our _tstate_lock.
1043 # This method passes its arguments to _tstate_lock.acquire().
1044 # If the lock is acquired, the C code is done, and self._stop() is
1045 # called. That sets ._is_stopped to True, and ._tstate_lock to None.
1046 lock = self._tstate_lock
1047 if lock is None: # already determined that the C code is done
1048 assert self._is_stopped
1049 elif lock.acquire(block, timeout):
1050 lock.release()
1051 self._stop()
1053 @property
1054 def name(self):
1055 """A string used for identification purposes only.
1057 It has no semantics. Multiple threads may be given the same name. The
1058 initial name is set by the constructor.
1060 """
1061 assert self._initialized, "Thread.__init__() not called"
1062 return self._name
1064 @name.setter
1065 def name(self, name):
1066 assert self._initialized, "Thread.__init__() not called"
1067 self._name = str(name)
1069 @property
1070 def ident(self):
1071 """Thread identifier of this thread or None if it has not been started.
1073 This is a nonzero integer. See the get_ident() function. Thread
1074 identifiers may be recycled when a thread exits and another thread is
1075 created. The identifier is available even after the thread has exited.
1077 """
1078 assert self._initialized, "Thread.__init__() not called"
1079 return self._ident
1081 if _HAVE_THREAD_NATIVE_ID:
1082 @property
1083 def native_id(self):
1084 """Native integral thread ID of this thread, or None if it has not been started.
1086 This is a non-negative integer. See the get_native_id() function.
1087 This represents the Thread ID as reported by the kernel.
1089 """
1090 assert self._initialized, "Thread.__init__() not called"
1091 return self._native_id
1093 def is_alive(self):
1094 """Return whether the thread is alive.
1096 This method returns True just before the run() method starts until just
1097 after the run() method terminates. The module function enumerate()
1098 returns a list of all alive threads.
1100 """
1101 assert self._initialized, "Thread.__init__() not called"
1102 if self._is_stopped or not self._started.is_set():
1103 return False
1104 self._wait_for_tstate_lock(False)
1105 return not self._is_stopped
1107 @property
1108 def daemon(self):
1109 """A boolean value indicating whether this thread is a daemon thread.
1111 This must be set before start() is called, otherwise RuntimeError is
1112 raised. Its initial value is inherited from the creating thread; the
1113 main thread is not a daemon thread and therefore all threads created in
1114 the main thread default to daemon = False.
1116 The entire Python program exits when only daemon threads are left.
1118 """
1119 assert self._initialized, "Thread.__init__() not called"
1120 return self._daemonic
1122 @daemon.setter
1123 def daemon(self, daemonic):
1124 if not self._initialized:
1125 raise RuntimeError("Thread.__init__() not called")
1126 if self._started.is_set():
1127 raise RuntimeError("cannot set daemon status of active thread")
1128 self._daemonic = daemonic
1130 def isDaemon(self):
1131 return self.daemon
1133 def setDaemon(self, daemonic):
1134 self.daemon = daemonic
1136 def getName(self):
1137 return self.name
1139 def setName(self, name):
1140 self.name = name
1143try:
1144 from _thread import (_excepthook as excepthook,
1145 _ExceptHookArgs as ExceptHookArgs)
1146except ImportError:
1147 # Simple Python implementation if _thread._excepthook() is not available
1148 from traceback import print_exception as _print_exception
1149 from collections import namedtuple
1151 _ExceptHookArgs = namedtuple(
1152 'ExceptHookArgs',
1153 'exc_type exc_value exc_traceback thread')
1155 def ExceptHookArgs(args):
1156 return _ExceptHookArgs(*args)
1158 def excepthook(args, /):
1159 """
1160 Handle uncaught Thread.run() exception.
1161 """
1162 if args.exc_type == SystemExit:
1163 # silently ignore SystemExit
1164 return
1166 if _sys is not None and _sys.stderr is not None:
1167 stderr = _sys.stderr
1168 elif args.thread is not None:
1169 stderr = args.thread._stderr
1170 if stderr is None:
1171 # do nothing if sys.stderr is None and sys.stderr was None
1172 # when the thread was created
1173 return
1174 else:
1175 # do nothing if sys.stderr is None and args.thread is None
1176 return
1178 if args.thread is not None:
1179 name = args.thread.name
1180 else:
1181 name = get_ident()
1182 print(f"Exception in thread {name}:",
1183 file=stderr, flush=True)
1184 _print_exception(args.exc_type, args.exc_value, args.exc_traceback,
1185 file=stderr)
1186 stderr.flush()
1189def _make_invoke_excepthook():
1190 # Create a local namespace to ensure that variables remain alive
1191 # when _invoke_excepthook() is called, even if it is called late during
1192 # Python shutdown. It is mostly needed for daemon threads.
1194 old_excepthook = excepthook
1195 old_sys_excepthook = _sys.excepthook
1196 if old_excepthook is None:
1197 raise RuntimeError("threading.excepthook is None")
1198 if old_sys_excepthook is None:
1199 raise RuntimeError("sys.excepthook is None")
1201 sys_exc_info = _sys.exc_info
1202 local_print = print
1203 local_sys = _sys
1205 def invoke_excepthook(thread):
1206 global excepthook
1207 try:
1208 hook = excepthook
1209 if hook is None:
1210 hook = old_excepthook
1212 args = ExceptHookArgs([*sys_exc_info(), thread])
1214 hook(args)
1215 except Exception as exc:
1216 exc.__suppress_context__ = True
1217 del exc
1219 if local_sys is not None and local_sys.stderr is not None:
1220 stderr = local_sys.stderr
1221 else:
1222 stderr = thread._stderr
1224 local_print("Exception in threading.excepthook:",
1225 file=stderr, flush=True)
1227 if local_sys is not None and local_sys.excepthook is not None:
1228 sys_excepthook = local_sys.excepthook
1229 else:
1230 sys_excepthook = old_sys_excepthook
1232 sys_excepthook(*sys_exc_info())
1233 finally:
1234 # Break reference cycle (exception stored in a variable)
1235 args = None
1237 return invoke_excepthook
1240# The timer class was contributed by Itamar Shtull-Trauring
1242class Timer(Thread):
1243 """Call a function after a specified number of seconds:
1245 t = Timer(30.0, f, args=None, kwargs=None)
1246 t.start()
1247 t.cancel() # stop the timer's action if it's still waiting
1249 """
1251 def __init__(self, interval, function, args=None, kwargs=None):
1252 Thread.__init__(self)
1253 self.interval = interval
1254 self.function = function
1255 self.args = args if args is not None else []
1256 self.kwargs = kwargs if kwargs is not None else {}
1257 self.finished = Event()
1259 def cancel(self):
1260 """Stop the timer if it hasn't finished yet."""
1261 self.finished.set()
1263 def run(self):
1264 self.finished.wait(self.interval)
1265 if not self.finished.is_set():
1266 self.function(*self.args, **self.kwargs)
1267 self.finished.set()
1270# Special thread class to represent the main thread
1272class _MainThread(Thread):
1274 def __init__(self):
1275 Thread.__init__(self, name="MainThread", daemon=False)
1276 self._set_tstate_lock()
1277 self._started.set()
1278 self._set_ident()
1279 if _HAVE_THREAD_NATIVE_ID:
1280 self._set_native_id()
1281 with _active_limbo_lock:
1282 _active[self._ident] = self
1285# Dummy thread class to represent threads not started here.
1286# These aren't garbage collected when they die, nor can they be waited for.
1287# If they invoke anything in threading.py that calls current_thread(), they
1288# leave an entry in the _active dict forever after.
1289# Their purpose is to return *something* from current_thread().
1290# They are marked as daemon threads so we won't wait for them
1291# when we exit (conform previous semantics).
1293class _DummyThread(Thread):
1295 def __init__(self):
1296 Thread.__init__(self, name=_newname("Dummy-%d"), daemon=True)
1298 self._started.set()
1299 self._set_ident()
1300 if _HAVE_THREAD_NATIVE_ID:
1301 self._set_native_id()
1302 with _active_limbo_lock:
1303 _active[self._ident] = self
1305 def _stop(self):
1306 pass
1308 def is_alive(self):
1309 assert not self._is_stopped and self._started.is_set()
1310 return True
1312 def join(self, timeout=None):
1313 assert False, "cannot join a dummy thread"
1316# Global API functions
1318def current_thread():
1319 """Return the current Thread object, corresponding to the caller's thread of control.
1321 If the caller's thread of control was not created through the threading
1322 module, a dummy thread object with limited functionality is returned.
1324 """
1325 try:
1326 return _active[get_ident()]
1327 except KeyError:
1328 return _DummyThread()
1330currentThread = current_thread
1332def active_count():
1333 """Return the number of Thread objects currently alive.
1335 The returned count is equal to the length of the list returned by
1336 enumerate().
1338 """
1339 with _active_limbo_lock:
1340 return len(_active) + len(_limbo)
1342activeCount = active_count
1344def _enumerate():
1345 # Same as enumerate(), but without the lock. Internal use only.
1346 return list(_active.values()) + list(_limbo.values())
1348def enumerate():
1349 """Return a list of all Thread objects currently alive.
1351 The list includes daemonic threads, dummy thread objects created by
1352 current_thread(), and the main thread. It excludes terminated threads and
1353 threads that have not yet been started.
1355 """
1356 with _active_limbo_lock:
1357 return list(_active.values()) + list(_limbo.values())
1360_threading_atexits = []
1361_SHUTTING_DOWN = False
1363def _register_atexit(func, *arg, **kwargs):
1364 """CPython internal: register *func* to be called before joining threads.
1366 The registered *func* is called with its arguments just before all
1367 non-daemon threads are joined in `_shutdown()`. It provides a similar
1368 purpose to `atexit.register()`, but its functions are called prior to
1369 threading shutdown instead of interpreter shutdown.
1371 For similarity to atexit, the registered functions are called in reverse.
1372 """
1373 if _SHUTTING_DOWN:
1374 raise RuntimeError("can't register atexit after shutdown")
1376 call = functools.partial(func, *arg, **kwargs)
1377 _threading_atexits.append(call)
1380from _thread import stack_size
1382# Create the main thread object,
1383# and make it available for the interpreter
1384# (Py_Main) as threading._shutdown.
1386_main_thread = _MainThread()
1388def _shutdown():
1389 """
1390 Wait until the Python thread state of all non-daemon threads get deleted.
1391 """
1392 # Obscure: other threads may be waiting to join _main_thread. That's
1393 # dubious, but some code does it. We can't wait for C code to release
1394 # the main thread's tstate_lock - that won't happen until the interpreter
1395 # is nearly dead. So we release it here. Note that just calling _stop()
1396 # isn't enough: other threads may already be waiting on _tstate_lock.
1397 if _main_thread._is_stopped:
1398 # _shutdown() was already called
1399 return
1401 global _SHUTTING_DOWN
1402 _SHUTTING_DOWN = True
1403 # Main thread
1404 tlock = _main_thread._tstate_lock
1405 # The main thread isn't finished yet, so its thread state lock can't have
1406 # been released.
1407 assert tlock is not None
1408 assert tlock.locked()
1409 tlock.release()
1410 _main_thread._stop()
1412 # Call registered threading atexit functions before threads are joined.
1413 # Order is reversed, similar to atexit.
1414 for atexit_call in reversed(_threading_atexits):
1415 atexit_call()
1417 # Join all non-deamon threads
1418 while True:
1419 with _shutdown_locks_lock:
1420 locks = list(_shutdown_locks)
1421 _shutdown_locks.clear()
1423 if not locks:
1424 break
1426 for lock in locks:
1427 # mimick Thread.join()
1428 lock.acquire()
1429 lock.release()
1431 # new threads can be spawned while we were waiting for the other
1432 # threads to complete
1435def main_thread():
1436 """Return the main thread object.
1438 In normal conditions, the main thread is the thread from which the
1439 Python interpreter was started.
1440 """
1441 return _main_thread
1443# get thread-local implementation, either from the thread
1444# module, or from the python fallback
1446try:
1447 from _thread import _local as local
1448except ImportError:
1449 from _threading_local import local
1452def _after_fork():
1453 """
1454 Cleanup threading module state that should not exist after a fork.
1455 """
1456 # Reset _active_limbo_lock, in case we forked while the lock was held
1457 # by another (non-forked) thread. http://bugs.python.org/issue874900
1458 global _active_limbo_lock, _main_thread
1459 global _shutdown_locks_lock, _shutdown_locks
1460 _active_limbo_lock = _allocate_lock()
1462 # fork() only copied the current thread; clear references to others.
1463 new_active = {}
1465 try:
1466 current = _active[get_ident()]
1467 except KeyError:
1468 # fork() was called in a thread which was not spawned
1469 # by threading.Thread. For example, a thread spawned
1470 # by thread.start_new_thread().
1471 current = _MainThread()
1473 _main_thread = current
1475 # reset _shutdown() locks: threads re-register their _tstate_lock below
1476 _shutdown_locks_lock = _allocate_lock()
1477 _shutdown_locks = set()
1479 with _active_limbo_lock:
1480 # Dangling thread instances must still have their locks reset,
1481 # because someone may join() them.
1482 threads = set(_enumerate())
1483 threads.update(_dangling)
1484 for thread in threads:
1485 # Any lock/condition variable may be currently locked or in an
1486 # invalid state, so we reinitialize them.
1487 if thread is current:
1488 # There is only one active thread. We reset the ident to
1489 # its new value since it can have changed.
1490 thread._reset_internal_locks(True)
1491 ident = get_ident()
1492 thread._ident = ident
1493 new_active[ident] = thread
1494 else:
1495 # All the others are already stopped.
1496 thread._reset_internal_locks(False)
1497 thread._stop()
1499 _limbo.clear()
1500 _active.clear()
1501 _active.update(new_active)
1502 assert len(_active) == 1
1505if hasattr(_os, "register_at_fork"):
1506 _os.register_at_fork(after_in_child=_after_fork)