"""Thread module emulating a subset of Java's threading model."""

import os as _os

import sys as _sys

import _thread

import warnings

from time import monotonic as _time

from _weakrefset import WeakSet

from itertools import count as _count

try:

from _collections import deque as _deque

except ImportError:

from collections import deque as _deque

# Note regarding PEP 8 compliant names

# This threading model was originally inspired by Java, and inherited

# the convention of camelCase function and method names from that

# language. Those original names are not in any imminent danger of

# being deprecated (even for Py3k),so this module provides them as an

# alias for the PEP 8 compliant names

# Note that using the new PEP 8 compliant names facilitates substitution

# with the multiprocessing module, which doesn't provide the old

# Java inspired names.

__all__ = ['get_ident', 'active_count', 'Condition', 'current_thread',

'enumerate', 'main_thread', 'TIMEOUT_MAX',

'Event', 'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Thread',

'Barrier', 'BrokenBarrierError', 'Timer', 'ThreadError',

'setprofile', 'settrace', 'local', 'stack_size',

'excepthook', 'ExceptHookArgs', 'gettrace', 'getprofile',

'setprofile_all_threads','settrace_all_threads']

# Rename some stuff so "from threading import *" is safe

_start_joinable_thread = _thread.start_joinable_thread

_daemon_threads_allowed = _thread.daemon_threads_allowed

_allocate_lock = _thread.allocate_lock

_LockType = _thread.LockType

_thread_shutdown = _thread._shutdown

_make_thread_handle = _thread._make_thread_handle

_ThreadHandle = _thread._ThreadHandle

get_ident = _thread.get_ident

_get_main_thread_ident = _thread._get_main_thread_ident

_is_main_interpreter = _thread._is_main_interpreter

try:

get_native_id = _thread.get_native_id

_HAVE_THREAD_NATIVE_ID = True

__all__.append('get_native_id')

except AttributeError:

_HAVE_THREAD_NATIVE_ID = False

ThreadError = _thread.error

try:

_CRLock = _thread.RLock

except AttributeError:

_CRLock = None

TIMEOUT_MAX = _thread.TIMEOUT_MAX

del _thread

# get thread-local implementation, either from the thread

# module, or from the python fallback

try:

from _thread import _local as local

except ImportError:

from _threading_local import local

# 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 setprofile_all_threads(func):

"""Set a profile function for all threads started from the threading module

and all Python threads that are currently executing.

The func will be passed to sys.setprofile() for each thread, before its

run() method is called.

"""

setprofile(func)

_sys._setprofileallthreads(func)

def getprofile():

"""Get the profiler function as set by threading.setprofile()."""

return _profile_hook

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

def settrace_all_threads(func):

"""Set a trace function for all threads started from the threading module

and all Python threads that are currently executing.

The func will be passed to sys.settrace() for each thread, before its run()

method is called.

"""

settrace(func)

_sys._settraceallthreads(func)

def gettrace():

"""Get the trace function as set by threading.settrace()."""

return _trace_hook

# Synchronization classes

Lock = _LockType

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.

"""

if args or kwargs:

warnings.warn(

'Passing arguments to RLock is deprecated and will be removed in 3.15',

DeprecationWarning,

stacklevel=2,

)

if _CRLock is None:

return _PyRLock(*args, **kwargs)

return _CRLock(*args, **kwargs)

class _RLock:

"""This class implements reentrant lock objects.

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):

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 %s.%s object owner=%r count=%d at %s>" % (

"locked" if self._block.locked() else "unlocked",

self.__class__.__module__,

self.__class__.__qualname__,

owner,

self._count,

hex(id(self))

)

def _at_fork_reinit(self):

self._block._at_fork_reinit()

self._owner = None

self._count = 0

def acquire(self, blocking=True, timeout=-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.

When invoked with the floating-point timeout argument set to a positive

value, block for at most the number of seconds specified by timeout

and as long as the lock cannot be acquired. Return true if the lock has

been acquired, false if the timeout has elapsed.

"""

me = get_ident()

if self._owner == me:

self._count += 1

return 1

rc = self._block.acquire(blocking, timeout)

if rc:

self._owner = me

self._count = 1

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()

def __exit__(self, t, v, tb):

self.release()

# Internal methods used by condition variables

def _acquire_restore(self, state):

self._block.acquire()

self._count, self._owner = state

def _release_save(self):

if self._count == 0:

raise RuntimeError("cannot release un-acquired lock")

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()

# Internal method used for reentrancy checks

def _recursion_count(self):

if self._owner != get_ident():

return 0

return self._count

_PyRLock = _RLock

class Condition:

"""Class that implements a condition variable.

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.

"""

def __init__(self, lock=None):

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().

if hasattr(lock, '_release_save'):

self._release_save = lock._release_save

if hasattr(lock, '_acquire_restore'):

self._acquire_restore = lock._acquire_restore

if hasattr(lock, '_is_owned'):

self._is_owned = lock._is_owned

self._waiters = _deque()

def _at_fork_reinit(self):

self._lock._at_fork_reinit()

self._waiters.clear()

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(False):

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 notify_all() 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()

gotit = False

try: # restore state no matter what (e.g., KeyboardInterrupt)

if timeout is None:

waiter.acquire()

gotit = True

else:

if timeout > 0:

gotit = waiter.acquire(True, timeout)

else:

gotit = waiter.acquire(False)

return gotit

finally:

self._acquire_restore(saved_state)

if not gotit:

try:

self._waiters.remove(waiter)

except ValueError:

pass

def wait_for(self, predicate, timeout=None):

"""Wait until a condition evaluates to True.

predicate should be a callable which result will be interpreted as a

boolean value. A timeout may be provided giving the maximum time to

wait.

"""

endtime = None

waittime = timeout

result = predicate()

while not result:

if waittime is not None:

if endtime is None:

endtime = _time() + waittime

else:

waittime = endtime - _time()

if waittime <= 0:

break

self.wait(waittime)

result = predicate()

return result

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

while waiters and n > 0:

waiter = waiters[0]

try:

waiter.release()

except RuntimeError:

# gh-92530: The previous call of notify() released the lock,

# but was interrupted before removing it from the queue.

# It can happen if a signal handler raises an exception,

# like CTRL+C which raises KeyboardInterrupt.

pass

else:

n -= 1

try:

waiters.remove(waiter)

except ValueError:

pass

def notify_all(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))

def notifyAll(self):

"""Wake up all threads waiting on this condition.

This method is deprecated, use notify_all() instead.

"""

import warnings

warnings.warn('notifyAll() is deprecated, use notify_all() instead',

DeprecationWarning, stacklevel=2)

self.notify_all()

class Semaphore:

"""This class implements semaphore objects.

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):

if value < 0:

raise ValueError("semaphore initial value must be >= 0")

self._cond = Condition(Lock())

self._value = value

def __repr__(self):

cls = self.__class__

return (f"<{cls.__module__}.{cls.__qualname__} at {id(self):#x}:"

f" value={self._value}>")

def acquire(self, blocking=True, timeout=None):

"""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.

When invoked with a timeout other than None, it will block for at

most timeout seconds. If acquire does not complete successfully in

that interval, return false. Return true otherwise.

"""

if not blocking and timeout is not None:

raise ValueError("can't specify timeout for non-blocking acquire")

rc = False

endtime = None

with self._cond:

while self._value == 0:

if not blocking:

break

if timeout is not None:

if endtime is None:

endtime = _time() + timeout

else:

timeout = endtime - _time()

if timeout <= 0:

break

self._cond.wait(timeout)

else:

self._value -= 1

rc = True

return rc

__enter__ = acquire

def release(self, n=1):

"""Release a semaphore, incrementing the internal counter by one or more.

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 n < 1:

raise ValueError('n must be one or more')

with self._cond:

self._value += n

self._cond.notify(n)

def __exit__(self, t, v, tb):

self.release()

class BoundedSemaphore(Semaphore):

"""Implements a 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.

"""

def __init__(self, value=1):

super().__init__(value)

self._initial_value = value

def __repr__(self):

cls = self.__class__

return (f"<{cls.__module__}.{cls.__qualname__} at {id(self):#x}:"

f" value={self._value}/{self._initial_value}>")

def release(self, n=1):

"""Release a semaphore, incrementing the internal counter by one or more.

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.

"""

if n < 1:

raise ValueError('n must be one or more')

with self._cond:

if self._value + n > self._initial_value:

raise ValueError("Semaphore released too many times")

self._value += n

self._cond.notify(n)

class Event:

"""Class implementing event objects.

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. The flag is initially false.

"""

# After Tim Peters' event class (without is_posted())

def __init__(self):

self._cond = Condition(Lock())

self._flag = False

def __repr__(self):

cls = self.__class__

status = 'set' if self._flag else 'unset'

return f"<{cls.__module__}.{cls.__qualname__} at {id(self):#x}: {status}>"

def _at_fork_reinit(self):

# Private method called by Thread._after_fork()

self._cond._at_fork_reinit()

def is_set(self):

"""Return true if and only if the internal flag is true."""

return self._flag

def isSet(self):

"""Return true if and only if the internal flag is true.

This method is deprecated, use is_set() instead.

"""

import warnings

warnings.warn('isSet() is deprecated, use is_set() instead',

DeprecationWarning, stacklevel=2)

return self.is_set()

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.

"""

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, when

it will return ``False``.

"""

with self._cond:

signaled = self._flag

if not signaled:

signaled = self._cond.wait(timeout)

return signaled

# A barrier class. Inspired in part by the pthread_barrier_* api and

# the CyclicBarrier class from Java. See

# http://sourceware.org/pthreads-win32/manual/pthread_barrier_init.html and

# http://java.sun.com/j2se/1.5.0/docs/api/java/util/concurrent/

# CyclicBarrier.html

# for information.

# We maintain two main states, 'filling' and 'draining' enabling the barrier

# to be cyclic. Threads are not allowed into it until it has fully drained

# since the previous cycle. In addition, a 'resetting' state exists which is

# similar to 'draining' except that threads leave with a BrokenBarrierError,

# and a 'broken' state in which all threads get the exception.

class Barrier:

"""Implements a Barrier.

Useful for synchronizing a fixed number of threads at known synchronization

points. Threads block on 'wait()' and are simultaneously awoken once they

have all made that call.

"""

def __init__(self, parties, action=None, timeout=None):

"""Create a barrier, initialised to 'parties' threads.

'action' is a callable which, when supplied, will be called by one of

the threads after they have all entered the barrier and just prior to

releasing them all. If a 'timeout' is provided, it is used as the

default for all subsequent 'wait()' calls.

"""

if parties < 1:

raise ValueError("parties must be >= 1")

self._cond = Condition(Lock())

self._action = action

self._timeout = timeout

self._parties = parties

self._state = 0 # 0 filling, 1 draining, -1 resetting, -2 broken

self._count = 0

def __repr__(self):

cls = self.__class__

if self.broken:

return f"<{cls.__module__}.{cls.__qualname__} at {id(self):#x}: broken>"

return (f"<{cls.__module__}.{cls.__qualname__} at {id(self):#x}:"

f" waiters={self.n_waiting}/{self.parties}>")

def wait(self, timeout=None):

"""Wait for the barrier.

When the specified number of threads have started waiting, they are all

simultaneously awoken. If an 'action' was provided for the barrier, one

of the threads will have executed that callback prior to returning.

Returns an individual index number from 0 to 'parties-1'.

"""

if timeout is None:

timeout = self._timeout

with self._cond:

self._enter() # Block while the barrier drains.

index = self._count

self._count += 1

try:

if index + 1 == self._parties:

# We release the barrier

self._release()

else:

# We wait until someone releases us

self._wait(timeout)

return index

finally:

self._count -= 1

# Wake up any threads waiting for barrier to drain.

self._exit()

# Block until the barrier is ready for us, or raise an exception

# if it is broken.

def _enter(self):

while self._state in (-1, 1):

# It is draining or resetting, wait until done

self._cond.wait()

#see if the barrier is in a broken state

if self._state < 0:

raise BrokenBarrierError

assert self._state == 0

# Optionally run the 'action' and release the threads waiting

# in the barrier.

def _release(self):

try:

if self._action:

self._action()

# enter draining state

self._state = 1

self._cond.notify_all()

except:

#an exception during the _action handler. Break and reraise

self._break()

raise

# Wait in the barrier until we are released. Raise an exception

# if the barrier is reset or broken.

def _wait(self, timeout):

if not self._cond.wait_for(lambda : self._state != 0, timeout):

#timed out. Break the barrier

self._break()

raise BrokenBarrierError

if self._state < 0:

raise BrokenBarrierError

assert self._state == 1

# If we are the last thread to exit the barrier, signal any threads

# waiting for the barrier to drain.

def _exit(self):

if self._count == 0:

if self._state in (-1, 1):

#resetting or draining

self._state = 0

self._cond.notify_all()

def reset(self):

"""Reset the barrier to the initial state.

Any threads currently waiting will get the BrokenBarrier exception

raised.

"""

with self._cond:

if self._count > 0:

if self._state == 0:

#reset the barrier, waking up threads

self._state = -1

elif self._state == -2:

#was broken, set it to reset state

#which clears when the last thread exits

self._state = -1

else:

self._state = 0

self._cond.notify_all()

def abort(self):

"""Place the barrier into a 'broken' state.

Useful in case of error. Any currently waiting threads and threads

attempting to 'wait()' will have BrokenBarrierError raised.

"""

with self._cond:

self._break()

def _break(self):

# An internal error was detected. The barrier is set to

# a broken state all parties awakened.

self._state = -2

self._cond.notify_all()

@property

def parties(self):

"""Return the number of threads required to trip the barrier."""

return self._parties

@property

def n_waiting(self):

"""Return the number of threads currently waiting at the barrier."""

# We don't need synchronization here since this is an ephemeral result

# anyway. It returns the correct value in the steady state.

if self._state == 0:

return self._count

return 0

@property

def broken(self):

"""Return True if the barrier is in a broken state."""

return self._state == -2

# exception raised by the Barrier class

class BrokenBarrierError(RuntimeError):

pass

# Helper to generate new thread names

_counter = _count(1).__next__

def _newname(name_template):

return name_template % _counter()

# Active thread administration.

#

# bpo-44422: Use a reentrant lock to allow reentrant calls to functions like

# threading.enumerate().

_active_limbo_lock = RLock()

_active = {} # maps thread id to Thread object

_limbo = {}

_dangling = WeakSet()

# Main class for threads

class Thread:

"""A class that represents a thread of control.

This class can be safely subclassed in a limited fashion. 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.

"""

_initialized = False

def __init__(self, group=None, target=None, name=None,

args=(), kwargs=None, *, daemon=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 a list or tuple of arguments 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"

if kwargs is None:

kwargs = {}

if name:

name = str(name)

else:

name = _newname("Thread-%d")

if target is not None:

try:

target_name = target.__name__

name += f" ({target_name})"

except AttributeError:

pass

self._target = target

self._name = name

self._args = args

self._kwargs = kwargs

if daemon is not None:

if daemon and not _daemon_threads_allowed():

raise RuntimeError('daemon threads are disabled in this (sub)interpreter')

self._daemonic = daemon

else:

self._daemonic = current_thread().daemon

self._ident = None

if _HAVE_THREAD_NATIVE_ID:

self._native_id = None

self._handle = _ThreadHandle()

self._started = Event()

self._initialized = True

# Copy of sys.stderr used by self._invoke_excepthook()

self._stderr = _sys.stderr

self._invoke_excepthook = _make_invoke_excepthook()

# For debugging and _after_fork()

_dangling.add(self)

def _after_fork(self, new_ident=None):

# Private! Called by threading._after_fork().

self._started._at_fork_reinit()

if new_ident is not None:

# This thread is alive.

self._ident = new_ident

assert self._handle.ident == new_ident

if _HAVE_THREAD_NATIVE_ID:

self._set_native_id()

else:

# Otherwise, the thread is dead, Jim. _PyThread_AfterFork()

# already marked our handle done.

pass

def __repr__(self):

assert self._initialized, "Thread.__init__() was not called"

status = "initial"

if self._started.is_set():

status = "started"

if self._handle.is_done():

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")

with _active_limbo_lock:

_limbo[self] = self

try:

# Start joinable thread

_start_joinable_thread(self._bootstrap, handle=self._handle,

daemon=self.daemon)

except Exception:

with _active_limbo_lock:

del _limbo[self]

raise

self._started.wait() # Will set ident and native_id

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 is not None:

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