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threading.py
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1321 lines (1064 loc) · 46 KB
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"""Thread module emulating a subset of Java's threading model."""
import sys as _sys
try:
import thread
except ImportError:
del _sys.modules[__name__]
raise
import warnings
from collections import deque as _deque
from itertools import count as _count
from time import time as _time, sleep as _sleep
from traceback import format_exc as _format_exc
# Note regarding PEP 8 compliant aliases
# This threading model was originally inspired by Java, and inherited
# the convention of camelCase function and method names from that
# language. While those names are not in any imminent danger of being
# deprecated, starting with Python 2.6, the module now provides a
# PEP 8 compliant alias for any such method name.
# Using the new PEP 8 compliant names also facilitates substitution
# with the multiprocessing module, which doesn't provide the old
# Java inspired names.
# Rename some stuff so "from threading import *" is safe
__all__ = ['activeCount', 'active_count', 'Condition', 'currentThread',
'current_thread', 'enumerate', 'Event',
'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Thread',
'Timer', 'setprofile', 'settrace', 'local', 'stack_size']
_start_new_thread = thread.start_new_thread
_allocate_lock = thread.allocate_lock
_get_ident = thread.get_ident
ThreadError = thread.error
del thread
# sys.exc_clear is used to work around the fact that except blocks
# don't fully clear the exception until 3.0.
warnings.filterwarnings('ignore', category=DeprecationWarning,
module='threading', message='sys.exc_clear')
# Debug support (adapted from ihooks.py).
# All the major classes here derive from _Verbose. We force that to
# be a new-style class so that all the major classes here are new-style.
# This helps debugging (type(instance) is more revealing for instances
# of new-style classes).
_VERBOSE = False
if __debug__:
class _Verbose(object):
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
# Issue #4188: calling current_thread() can incur an infinite
# recursion if it has to create a DummyThread on the fly.
ident = _get_ident()
try:
name = _active[ident].name
except KeyError:
name = "<OS thread %d>" % ident
format = "%s: %s\n" % (name, format)
_sys.stderr.write(format)
else:
# Disable this when using "python -O"
class _Verbose(object):
def __init__(self, verbose=None):
pass
def _note(self, *args):
pass
# Support for profile and trace hooks
_profile_hook = None
_trace_hook = None
def setprofile(func):
"""Set a profile function for all threads started from the threading module.
The func will be passed to sys.setprofile() for each thread, before its
run() method is called.
"""
global _profile_hook
_profile_hook = func
def settrace(func):
"""Set a trace function for all threads started from the threading module.
The func will be passed to sys.settrace() for each thread, before its run()
method is called.
"""
global _trace_hook
_trace_hook = func
# Synchronization classes
Lock = _allocate_lock
def RLock(*args, **kwargs):
"""Factory function that returns a new reentrant lock.
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.
"""
return _RLock(*args, **kwargs)
class _RLock(_Verbose):
"""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.
"""
def __init__(self, verbose=None):
_Verbose.__init__(self, verbose)
self.__block = _allocate_lock()
self.__owner = None
self.__count = 0
def __repr__(self):
owner = self.__owner
try:
owner = _active[owner].name
except KeyError:
pass
return "<%s owner=%r count=%d>" % (
self.__class__.__name__, owner, self.__count)
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 an argument would block, return false immediately;
otherwise, do the same thing as when called without arguments, and
return true.
"""
me = _get_ident()
if self.__owner == 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 success", self, blocking)
else:
if __debug__:
self._note("%s.acquire(%s): failure", self, blocking)
return rc
__enter__ = acquire
def release(self):
"""Release a lock, decrementing the recursion level.
If after the decrement it is zero, reset the lock to unlocked (not owned
by any thread), and if any other threads are blocked waiting for the
lock to become unlocked, allow exactly one of them to proceed. If after
the decrement the recursion level is still nonzero, the lock remains
locked and owned by the calling thread.
Only call this method when the calling thread owns the lock. A
RuntimeError is raised if this method is called when the lock is
unlocked.
There is no return value.
"""
if self.__owner != _get_ident():
raise RuntimeError("cannot release un-acquired 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)
def __exit__(self, t, v, tb):
self.release()
# Internal methods used by condition variables
def _acquire_restore(self, count_owner):
count, owner = 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 == _get_ident()
def Condition(*args, **kwargs):
"""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.
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.
"""
return _Condition(*args, **kwargs)
class _Condition(_Verbose):
"""Condition variables allow one or more threads to wait until they are
notified by another thread.
"""
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 __enter__(self):
return self.__lock.__enter__()
def __exit__(self, *args):
return self.__lock.__exit__(*args)
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):
# Return True if lock is owned by current_thread.
# This method is called only if __lock doesn't have _is_owned().
if self.__lock.acquire(0):
self.__lock.release()
return False
else:
return True
def wait(self, timeout=None):
"""Wait until notified or until a timeout occurs.
If the calling thread has not acquired the lock when this method is
called, a RuntimeError is raised.
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.
"""
if not self._is_owned():
raise RuntimeError("cannot wait on un-acquired lock")
waiter = _allocate_lock()
waiter.acquire()
self.__waiters.append(waiter)
saved_state = self._release_save()
try: # restore state no matter what (e.g., KeyboardInterrupt)
if timeout is None:
waiter.acquire()
if __debug__:
self._note("%s.wait(): got it", self)
else:
# Balancing act: We can't afford a pure busy loop, so we
# have to sleep; but if we sleep the whole timeout time,
# we'll be unresponsive. The scheme here sleeps very
# little at first, longer as time goes on, but never longer
# than 20 times per second (or the timeout time remaining).
endtime = _time() + timeout
delay = 0.0005 # 500 us -> initial delay of 1 ms
while True:
gotit = waiter.acquire(0)
if gotit:
break
remaining = endtime - _time()
if remaining <= 0:
break
delay = min(delay * 2, remaining, .05)
_sleep(delay)
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)
finally:
self._acquire_restore(saved_state)
def notify(self, n=1):
"""Wake up one or more threads waiting on this condition, if any.
If the calling thread has not acquired the lock when this method is
called, a RuntimeError is raised.
This method wakes up at most n of the threads waiting for the condition
variable; it is a no-op if no threads are waiting.
"""
if not self._is_owned():
raise RuntimeError("cannot notify on un-acquired 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):
"""Wake up all threads waiting on this condition.
If the calling thread has not acquired the lock when this method
is called, a RuntimeError is raised.
"""
self.notify(len(self.__waiters))
notify_all = notifyAll
def Semaphore(*args, **kwargs):
"""A factory function that returns a new semaphore.
Semaphores manage 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. If not given, value defaults to 1.
"""
return _Semaphore(*args, **kwargs)
class _Semaphore(_Verbose):
"""Semaphores manage 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. If not given, value defaults to 1.
"""
# After Tim Peters' semaphore class, but not quite the same (no maximum)
def __init__(self, value=1, verbose=None):
if value < 0:
raise ValueError("semaphore initial value must be >= 0")
_Verbose.__init__(self, verbose)
self.__cond = Condition(Lock())
self.__value = value
def acquire(self, blocking=1):
"""Acquire a semaphore, decrementing the internal counter by one.
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 blocking set to true, do the same thing as when called
without arguments, and return true.
When invoked with blocking set to false, do not block. If a call without
an argument would block, return false immediately; otherwise, do the
same thing as when called without arguments, and return true.
"""
rc = False
with self.__cond:
while self.__value == 0:
if not blocking:
break
if __debug__:
self._note("%s.acquire(%s): blocked waiting, value=%s",
self, blocking, self.__value)
self.__cond.wait()
else:
self.__value = self.__value - 1
if __debug__:
self._note("%s.acquire: success, value=%s",
self, self.__value)
rc = True
return rc
__enter__ = acquire
def release(self):
"""Release a semaphore, incrementing the internal counter by one.
When the counter is zero on entry and another thread is waiting for it
to become larger than zero again, wake up that thread.
"""
with self.__cond:
self.__value = self.__value + 1
if __debug__:
self._note("%s.release: success, value=%s",
self, self.__value)
self.__cond.notify()
def __exit__(self, t, v, tb):
self.release()
def BoundedSemaphore(*args, **kwargs):
"""A factory function that returns a new bounded semaphore.
A bounded semaphore checks to make sure its current value doesn't exceed its
initial value. If it does, ValueError is raised. In most situations
semaphores are used to guard resources with limited capacity.
If the semaphore is released too many times it's a sign of a bug. If not
given, value defaults to 1.
Like regular semaphores, bounded semaphores manage 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. If not given, value defaults to 1.
"""
return _BoundedSemaphore(*args, **kwargs)
class _BoundedSemaphore(_Semaphore):
"""A bounded semaphore checks to make sure its current value doesn't exceed
its initial value. If it does, ValueError is raised. In most situations
semaphores are used to guard resources with limited capacity.
"""
def __init__(self, value=1, verbose=None):
_Semaphore.__init__(self, value, verbose)
self._initial_value = value
def release(self):
"""Release a semaphore, incrementing the internal counter by one.
When the counter is zero on entry and another thread is waiting for it
to become larger than zero again, wake up that thread.
If the number of releases exceeds the number of acquires,
raise a ValueError.
"""
with self._Semaphore__cond:
if self._Semaphore__value >= self._initial_value:
raise ValueError("Semaphore released too many times")
self._Semaphore__value += 1
self._Semaphore__cond.notify()
def Event(*args, **kwargs):
"""A factory function that returns a new event.
Events manage 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.
"""
return _Event(*args, **kwargs)
class _Event(_Verbose):
"""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.
"""
# After Tim Peters' event class (without is_posted())
def __init__(self, verbose=None):
_Verbose.__init__(self, verbose)
self.__cond = Condition(Lock())
self.__flag = False
def _reset_internal_locks(self):
# private! called by Thread._reset_internal_locks by _after_fork()
self.__cond.__init__(Lock())
def isSet(self):
'Return true if and only if the internal flag is true.'
return self.__flag
is_set = isSet
def set(self):
"""Set the internal flag to true.
All threads waiting for the flag to become true are awakened. Threads
that call wait() once the flag is true will not block at all.
"""
with self.__cond:
self.__flag = True
self.__cond.notify_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.
"""
with self.__cond:
self.__flag = False
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).
This method returns the internal flag on exit, so it will always return
True except if a timeout is given and the operation times out.
"""
with self.__cond:
if not self.__flag:
self.__cond.wait(timeout)
return self.__flag
# Helper to generate new thread names
_counter = _count().next
_counter() # Consume 0 so first non-main thread has id 1.
def _newname(template="Thread-%d"):
return template % _counter()
# Active thread administration
_active_limbo_lock = _allocate_lock()
_active = {} # maps thread id to Thread object
_limbo = {}
# Main class for threads
class Thread(_Verbose):
"""A class that represents a thread of control.
This class can be safely subclassed in a limited fashion.
"""
__initialized = False
# Need to store a reference to sys.exc_info for printing
# out exceptions when a thread tries to use a global var. during interp.
# shutdown and thus raises an exception about trying to perform some
# operation on/with a NoneType
__exc_info = _sys.exc_info
# Keep sys.exc_clear too to clear the exception just before
# allowing .join() to return.
__exc_clear = _sys.exc_clear
def __init__(self, group=None, target=None, name=None,
args=(), kwargs=None, verbose=None):
"""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* is the callable object to be invoked by the run()
method. Defaults to None, meaning nothing is called.
*name* is the thread name. By default, a unique name is constructed of
the form "Thread-N" where N is a small decimal number.
*args* is the argument tuple for the target invocation. Defaults to ().
*kwargs* is a dictionary of keyword arguments for the target
invocation. Defaults to {}.
If a subclass overrides the constructor, it must make sure to invoke
the base class constructor (Thread.__init__()) before doing anything
else to the thread.
"""
assert group is None, "group argument must be None for now"
_Verbose.__init__(self, verbose)
if kwargs is None:
kwargs = {}
self.__target = target
self.__name = str(name or _newname())
self.__args = args
self.__kwargs = kwargs
self.__daemonic = self._set_daemon()
self.__ident = None
self.__started = Event()
self.__stopped = False
self.__block = Condition(Lock())
self.__initialized = True
# sys.stderr is not stored in the class like
# sys.exc_info since it can be changed between instances
self.__stderr = _sys.stderr
def _reset_internal_locks(self):
# private! Called by _after_fork() to reset our internal locks as
# they may be in an invalid state leading to a deadlock or crash.
if hasattr(self, '_Thread__block'): # DummyThread deletes self.__block
self.__block.__init__()
self.__started._reset_internal_locks()
@property
def _block(self):
# used by a unittest
return self.__block
def _set_daemon(self):
# Overridden in _MainThread and _DummyThread
return current_thread().daemon
def __repr__(self):
assert self.__initialized, "Thread.__init__() was not called"
status = "initial"
if self.__started.is_set():
status = "started"
if self.__stopped:
status = "stopped"
if self.__daemonic:
status += " daemon"
if self.__ident is not None:
status += " %s" % self.__ident
return "<%s(%s, %s)>" % (self.__class__.__name__, self.__name, status)
def start(self):
"""Start the thread's activity.
It 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.
This method will raise a RuntimeError if called more than once on the
same thread object.
"""
if not self.__initialized:
raise RuntimeError("thread.__init__() not called")
if self.__started.is_set():
raise RuntimeError("threads can only be started once")
if __debug__:
self._note("%s.start(): starting thread", self)
with _active_limbo_lock:
_limbo[self] = self
try:
_start_new_thread(self.__bootstrap, ())
except Exception:
with _active_limbo_lock:
del _limbo[self]
raise
self.__started.wait()
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 to the object's constructor as the
target argument, if any, with sequential and keyword arguments taken
from the args and kwargs arguments, respectively.
"""
try:
if self.__target:
self.__target(*self.__args, **self.__kwargs)
finally:
# Avoid a refcycle if the thread is running a function with
# an argument that has a member that points to the thread.
del self.__target, self.__args, self.__kwargs
def __bootstrap(self):
# Wrapper around the real bootstrap code that ignores
# exceptions during interpreter cleanup. Those typically
# happen when a daemon thread wakes up at an unfortunate
# moment, finds the world around it destroyed, and raises some
# random exception *** while trying to report the exception in
# __bootstrap_inner() below ***. Those random exceptions
# don't help anybody, and they confuse users, so we suppress
# them. We suppress them only when it appears that the world
# indeed has already been destroyed, so that exceptions in
# __bootstrap_inner() during normal business hours are properly
# reported. Also, we only suppress them for daemonic threads;
# if a non-daemonic encounters this, something else is wrong.
try:
self.__bootstrap_inner()
except:
if self.__daemonic and _sys is None:
return
raise
def _set_ident(self):
self.__ident = _get_ident()
def __bootstrap_inner(self):
try:
self._set_ident()
self.__started.set()
with _active_limbo_lock:
_active[self.__ident] = self
del _limbo[self]
if __debug__:
self._note("%s.__bootstrap(): thread started", self)
if _trace_hook:
self._note("%s.__bootstrap(): registering trace hook", self)
_sys.settrace(_trace_hook)
if _profile_hook:
self._note("%s.__bootstrap(): registering profile hook", self)
_sys.setprofile(_profile_hook)
try:
self.run()
except SystemExit:
if __debug__:
self._note("%s.__bootstrap(): raised SystemExit", self)
except:
if __debug__:
self._note("%s.__bootstrap(): unhandled exception", self)
# If sys.stderr is no more (most likely from interpreter
# shutdown) use self.__stderr. Otherwise still use sys (as in
# _sys) in case sys.stderr was redefined since the creation of
# self.
if _sys and _sys.stderr is not None:
print>>_sys.stderr, ("Exception in thread %s:\n%s" %
(self.name, _format_exc()))
elif self.__stderr is not None:
# Do the best job possible w/o a huge amt. of code to
# approximate a traceback (code ideas from
# Lib/traceback.py)
exc_type, exc_value, exc_tb = self.__exc_info()
try:
print>>self.__stderr, (
"Exception in thread " + self.name +
" (most likely raised during interpreter shutdown):")
print>>self.__stderr, (
"Traceback (most recent call last):")
while exc_tb:
print>>self.__stderr, (
' File "%s", line %s, in %s' %
(exc_tb.tb_frame.f_code.co_filename,
exc_tb.tb_lineno,
exc_tb.tb_frame.f_code.co_name))
exc_tb = exc_tb.tb_next
print>>self.__stderr, ("%s: %s" % (exc_type, exc_value))
# Make sure that exc_tb gets deleted since it is a memory
# hog; deleting everything else is just for thoroughness
finally:
del exc_type, exc_value, exc_tb
else:
if __debug__:
self._note("%s.__bootstrap(): normal return", self)
finally:
# Prevent a race in
# test_threading.test_no_refcycle_through_target when
# the exception keeps the target alive past when we
# assert that it's dead.
self.__exc_clear()
finally:
with _active_limbo_lock:
self.__stop()
try:
# We don't call self.__delete() because it also
# grabs _active_limbo_lock.
del _active[_get_ident()]
except:
pass
def __stop(self):
# DummyThreads delete self.__block, but they have no waiters to
# notify anyway (join() is forbidden on them).
if not hasattr(self, '_Thread__block'):
return
self.__block.acquire()
self.__stopped = True
self.__block.notify_all()
self.__block.release()
def __delete(self):
"Remove current thread from the dict of currently running threads."
# Notes about running with dummy_thread:
#
# Must take care to not raise an exception if dummy_thread is being
# used (and thus this module is being used as an instance of
# dummy_threading). dummy_thread.get_ident() always returns -1 since
# there is only one thread if dummy_thread is being used. Thus
# len(_active) is always <= 1 here, and any Thread instance created
# overwrites the (if any) thread currently registered in _active.
#
# An instance of _MainThread is always created by 'threading'. This
# gets overwritten the instant an instance of Thread is created; both
# threads return -1 from dummy_thread.get_ident() and thus have the
# same key in the dict. So when the _MainThread instance created by
# 'threading' tries to clean itself up when atexit calls this method
# it gets a KeyError if another Thread instance was created.
#
# This all means that KeyError from trying to delete something from
# _active if dummy_threading is being used is a red herring. But
# since it isn't if dummy_threading is *not* being used then don't
# hide the exception.
try:
with _active_limbo_lock:
del _active[_get_ident()]
# There must not be any python code between the previous line
# and after the lock is released. Otherwise a tracing function
# could try to acquire the lock again in the same thread, (in
# current_thread()), and would block.
except KeyError:
if 'dummy_threading' not in _sys.modules:
raise
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). As join() always returns None, you must call
isAlive() after join() to decide whether a timeout happened -- if the
thread is still alive, the join() call timed out.
When the timeout argument is not present or None, the operation will
block until the thread terminates.
A thread can be join()ed many times.
join() raises a RuntimeError if an attempt is made to join the current
thread as that would cause a deadlock. It is also an error to join() a
thread before it has been started and attempts to do so raises the same
exception.
"""
if not self.__initialized:
raise RuntimeError("Thread.__init__() not called")
if not self.__started.is_set():
raise RuntimeError("cannot join thread before it is started")
if self is current_thread():
raise RuntimeError("cannot join current thread")
if __debug__:
if not self.__stopped:
self._note("%s.join(): waiting until thread stops", self)
self.__block.acquire()
try:
if timeout is None:
while not self.__stopped:
self.__block.wait()
if __debug__:
self._note("%s.join(): thread stopped", self)
else:
deadline = _time() + timeout
while not self.__stopped:
delay = deadline - _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)
finally:
self.__block.release()
@property
def name(self):
"""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.
"""
assert self.__initialized, "Thread.__init__() not called"
return self.__name
@name.setter
def name(self, name):
assert self.__initialized, "Thread.__init__() not called"
self.__name = str(name)
@property
def ident(self):
"""Thread identifier of this thread or None if it has not been started.
This is a nonzero integer. See the thread.get_ident() function. Thread
identifiers may be recycled when a thread exits and another thread is
created. The identifier is available even after the thread has exited.
"""
assert self.__initialized, "Thread.__init__() not called"
return self.__ident
def isAlive(self):
"""Return whether the thread is alive.
This method returns True just before the run() method starts until just
after the run() method terminates. The module function enumerate()
returns a list of all alive threads.
"""
assert self.__initialized, "Thread.__init__() not called"
return self.__started.is_set() and not self.__stopped
is_alive = isAlive
@property
def daemon(self):