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#Copyright (c) 2004-2005, CherryPy Team (team@cherrypy.org)
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#Redistribution and use in source and binary forms, with or without
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#modification, are permitted provided that the following conditions are met:
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# * Redistributions of source code must retain the above copyright notice,
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# this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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# * Neither the name of the CherryPy Team nor the names of its contributors
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# may be used to endorse or promote products derived from this software
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# without specific prior written permission.
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#THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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#ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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#WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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#DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
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#FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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#DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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#SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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#CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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#OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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#OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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# This is a backport of Python-2.4's threading.local() implementation
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"""Thread-local objects
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(Note that this module provides a Python version of thread
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threading.local class. Depending on the version of Python you're
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using, there may be a faster one available. You should always import
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the local class from threading.)
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Thread-local objects support the management of thread-local data.
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If you have data that you want to be local to a thread, simply create
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a thread-local object and use its attributes:
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>>> mydata.number = 42
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You can also access the local-object's dictionary:
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>>> mydata.__dict__.setdefault('widgets', [])
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What's important about thread-local objects is that their data are
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local to a thread. If we access the data in a different thread:
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... items = mydata.__dict__.items()
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... mydata.number = 11
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... log.append(mydata.number)
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>>> thread = threading.Thread(target=f)
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we get different data. Furthermore, changes made in the other thread
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don't affect data seen in this thread:
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Of course, values you get from a local object, including a __dict__
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attribute, are for whatever thread was current at the time the
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attribute was read. For that reason, you generally don't want to save
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these values across threads, as they apply only to the thread they
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You can create custom local objects by subclassing the local class:
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>>> class MyLocal(local):
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... initialized = False
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... def __init__(self, **kw):
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... if self.initialized:
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... raise SystemError('__init__ called too many times')
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... self.initialized = True
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... self.__dict__.update(kw)
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... def squared(self):
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... return self.number ** 2
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This can be useful to support default values, methods and
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initialization. Note that if you define an __init__ method, it will be
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called each time the local object is used in a separate thread. This
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is necessary to initialize each thread's dictionary.
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Now if we create a local object:
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>>> mydata = MyLocal(color='red')
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Now we have a default number:
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And a method that operates on the data:
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As before, we can access the data in a separate thread:
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>>> thread = threading.Thread(target=f)
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[[('color', 'red'), ('initialized', True)], 11]
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without affecting this thread's data:
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Traceback (most recent call last):
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AttributeError: 'MyLocal' object has no attribute 'color'
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Note that subclasses can define slots, but they are not thread
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local. They are shared across threads:
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>>> class MyLocal(local):
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... __slots__ = 'number'
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>>> mydata = MyLocal()
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>>> mydata.number = 42
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>>> mydata.color = 'red'
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So, the separate thread:
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>>> thread = threading.Thread(target=f)
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# Threading import is at end
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class _localbase(object):
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__slots__ = '_local__key', '_local__args', '_local__lock'
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def __new__(cls, *args, **kw):
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self = object.__new__(cls)
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key = '_local__key', 'thread.local.' + str(id(self))
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object.__setattr__(self, '_local__key', key)
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object.__setattr__(self, '_local__args', (args, kw))
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object.__setattr__(self, '_local__lock', RLock())
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if args or kw and (cls.__init__ is object.__init__):
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raise TypeError("Initialization arguments are not supported")
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# We need to create the thread dict in anticipation of
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# __init__ being called, to make sure we don't call it
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dict = object.__getattribute__(self, '__dict__')
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currentThread().__dict__[key] = dict
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key = object.__getattribute__(self, '_local__key')
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d = currentThread().__dict__.get(key)
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currentThread().__dict__[key] = d
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object.__setattr__(self, '__dict__', d)
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# we have a new instance dict, so call out __init__ if we have
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if cls.__init__ is not object.__init__:
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args, kw = object.__getattribute__(self, '_local__args')
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cls.__init__(self, *args, **kw)
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object.__setattr__(self, '__dict__', d)
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class local(_localbase):
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def __getattribute__(self, name):
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lock = object.__getattribute__(self, '_local__lock')
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return object.__getattribute__(self, name)
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def __setattr__(self, name, value):
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lock = object.__getattribute__(self, '_local__lock')
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return object.__setattr__(self, name, value)
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def __delattr__(self, name):
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lock = object.__getattribute__(self, '_local__lock')
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return object.__delattr__(self, name)
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threading_enumerate = enumerate
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__getattribute__ = object.__getattribute__
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key = __getattribute__(self, '_local__key')
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threads = list(threading_enumerate())
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# if enumerate fails, as it seems to do during
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# shutdown, we'll skip cleanup under the assumption
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# that there is nothing to clean up
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for thread in threads:
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__dict__ = thread.__dict__
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except AttributeError:
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# Thread is dying, rest in peace
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pass # didn't have anything in this thread
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from threading import currentThread, enumerate, RLock
added
removed
bin/tools/threadinglocal.py
