Implemented thread-local data as proposed on python-dev:
http://mail.python.org/pipermail/python-dev/2004-June/045785.html
This commit is contained in:
Jim Fulton
parent
e827437f45
commit
d15dc06df0
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@ -49,6 +49,25 @@ reset to false with the \method{clear()} method. The \method{wait()}
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method blocks until the flag is true.
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\end{funcdesc}
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\begin{classdesc*}{local}{}
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A class that represents thread-local data. Thread-local data are data
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who's values are thread specific. To manage thread-local data, just
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create an instance of \class{local} (or a subclass) and store
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attributes on it:
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\begin{verbatim}
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>>> mydata = threading.local()
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>>> mydata.x = 1
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\end{verbatim}
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The instance's values will be different for separate threads.
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For more details and extensive examples, see the documentation string
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of the _threading_local module.
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\versionadded{2.4}
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\end{classdesc*}
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\begin{funcdesc}{Lock}{}
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A factory function that returns a new primitive lock object. Once
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a thread has acquired it, subsequent attempts to acquire it block,
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@ -0,0 +1,237 @@
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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. Deoending 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 it's attributes:
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>>> mydata = local()
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>>> mydata.number = 42
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>>> mydata.number
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42
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You can also access the local-object's dictionary:
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>>> mydata.__dict__
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{'number': 42}
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>>> mydata.__dict__.setdefault('widgets', [])
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[]
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>>> mydata.widgets
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[]
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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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>>> log = []
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>>> def f():
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... items = mydata.__dict__.items()
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... items.sort()
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... log.append(items)
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... mydata.number = 11
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... log.append(mydata.number)
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>>> import threading
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>>> thread = threading.Thread(target=f)
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>>> thread.start()
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>>> thread.join()
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>>> log
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[[], 11]
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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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>>> mydata.number
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42
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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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came from.
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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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... number = 2
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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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>>> mydata.number
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2
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an initial color:
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>>> mydata.color
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'red'
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>>> del mydata.color
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And a method that operates on the data:
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>>> mydata.squared()
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4
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As before, we can access the data in a separate thread:
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>>> log = []
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>>> thread = threading.Thread(target=f)
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>>> thread.start()
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>>> thread.join()
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>>> log
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[[('color', 'red'), ('initialized', True)], 11]
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without effecting this threads data:
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>>> mydata.number
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2
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>>> mydata.color
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Traceback (most recent call last):
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...
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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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>>> thread.start()
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>>> thread.join()
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affects what we see:
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>>> mydata.number
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11
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>>> del mydata
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"""
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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 sire we don't cal it
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# again ourselves.
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dict = object.__getattribute__(self, '__dict__')
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currentThread().__dict__[key] = dict
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return self
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def _patch(self):
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key = object.__getattribute__(self, '_local__key')
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d = currentThread().__dict__.get(key)
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if d is None:
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d = {}
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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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# one
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cls = type(self)
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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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else:
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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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lock.acquire()
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try:
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_patch(self)
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return object.__getattribute__(self, name)
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finally:
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lock.release()
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def __setattr__(self, name, value):
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lock = object.__getattribute__(self, '_local__lock')
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lock.acquire()
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try:
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_patch(self)
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return object.__setattr__(self, name, value)
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finally:
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lock.release()
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def __delattr__(self, name):
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lock = object.__getattribute__(self, '_local__lock')
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lock.acquire()
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try:
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_patch(self)
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return object.__delattr__(self, name)
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finally:
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lock.release()
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def __del__():
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threading_enumerate = enumerate
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__getattribute__ = object.__getattribute__
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def __del__(self):
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key = __getattribute__(self, '_local__key')
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try:
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threads = list(threading_enumerate())
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except:
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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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return
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for thread in threads:
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try:
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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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continue
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if key in __dict__:
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try:
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del __dict__[key]
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except KeyError:
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pass # didn't have nything in this thread
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return __del__
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__del__ = __del__()
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from threading import currentThread, enumerate, RLock
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@ -18,6 +18,7 @@ import dummy_thread
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# Declaring now so as to not have to nest ``try``s to get proper clean-up.
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holding_thread = False
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holding_threading = False
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holding__threading_local = False
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try:
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# Could have checked if ``thread`` was not in sys.modules and gone
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@ -37,20 +38,39 @@ try:
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held_threading = sys_modules['threading']
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holding_threading = True
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del sys_modules['threading']
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if '_threading_local' in sys_modules:
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# If ``_threading_local`` is already imported, might as well prevent
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# trying to import it more than needed by saving it if it is
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# already imported before deleting it.
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held__threading_local = sys_modules['_threading_local']
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holding__threading_local = True
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del sys_modules['_threading_local']
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import threading
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# Need a copy of the code kept somewhere...
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sys_modules['_dummy_threading'] = sys_modules['threading']
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del sys_modules['threading']
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sys_modules['_dummy__threading_local'] = sys_modules['_threading_local']
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del sys_modules['_threading_local']
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from _dummy_threading import *
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from _dummy_threading import __all__
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finally:
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# Put back ``threading`` if we overwrote earlier
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if holding_threading:
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sys_modules['threading'] = held_threading
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del held_threading
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del holding_threading
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# Put back ``_threading_local`` if we overwrote earlier
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if holding__threading_local:
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sys_modules['_threading_local'] = held__threading_local
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del held__threading_local
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del holding__threading_local
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# Put back ``thread`` if we overwrote, else del the entry we made
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if holding_thread:
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sys_modules['thread'] = held_thread
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@ -0,0 +1,26 @@
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import unittest
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from doctest import DocTestSuite
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from test import test_support
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def test_main():
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suite = DocTestSuite('_threading_local')
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try:
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from thread import _local
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except ImportError:
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pass
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else:
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import _threading_local
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local_orig = _threading_local.local
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def setUp():
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_threading_local.local = _local
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def tearDown():
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_threading_local.local = local_orig
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suite.addTest(DocTestSuite('_threading_local',
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setUp=setUp, tearDown=tearDown)
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)
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test_support.run_suite(suite)
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if __name__ == '__main__':
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test_main()
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@ -15,7 +15,7 @@ from collections import deque
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# Rename some stuff so "from threading import *" is safe
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__all__ = ['activeCount', 'Condition', 'currentThread', 'enumerate', 'Event',
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'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Thread',
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'Timer', 'setprofile', 'settrace']
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'Timer', 'setprofile', 'settrace', 'local']
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_start_new_thread = thread.start_new_thread
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_allocate_lock = thread.allocate_lock
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@ -661,6 +661,14 @@ def enumerate():
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_MainThread()
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# get thread-local implementation, either from the thread
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# module, or from the python fallback
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try:
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from thread import _local as local
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except ImportError:
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from _threading_local import local
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# Self-test code
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@ -158,6 +158,259 @@ static PyTypeObject Locktype = {
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0, /*tp_repr*/
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};
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/* Thread-local objects */
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#include "structmember.h"
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typedef struct {
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PyObject_HEAD
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PyObject *key;
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PyObject *args;
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PyObject *kw;
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PyObject *dict;
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} localobject;
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static PyTypeObject localtype;
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static PyObject *
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local_new(PyTypeObject *type, PyObject *args, PyObject *kw)
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{
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localobject *self;
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PyObject *tdict;
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if (type->tp_init == PyBaseObject_Type.tp_init
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&& ((args && PyObject_IsTrue(args))
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||
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(kw && PyObject_IsTrue(kw))
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)
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) {
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PyErr_SetString(PyExc_TypeError,
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"Initialization arguments are not supported");
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return NULL;
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}
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self = (localobject *)type->tp_alloc(type, 0);
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if (self == NULL)
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return NULL;
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Py_XINCREF(args);
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self->args = args;
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Py_XINCREF(kw);
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self->kw = kw;
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self->dict = NULL; /* making sure */
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self->key = PyString_FromFormat("thread.local.%p", self);
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if (self->key == NULL)
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goto err;
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self->dict = PyDict_New();
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if (self->dict == NULL)
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goto err;
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tdict = PyThreadState_GetDict();
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if (tdict == NULL) {
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PyErr_SetString(PyExc_SystemError,
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"Couldn't get thread-state dictionary");
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goto err;
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}
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if (PyDict_SetItem(tdict, self->key, self->dict) < 0)
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goto err;
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return (PyObject *)self;
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err:
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Py_DECREF(self);
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return NULL;
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}
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static int
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local_traverse(localobject *self, visitproc visit, void *arg)
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{
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Py_VISIT(self->args);
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Py_VISIT(self->kw);
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Py_VISIT(self->dict);
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return 0;
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}
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static int
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local_clear(localobject *self)
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{
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Py_CLEAR(self->key);
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Py_CLEAR(self->args);
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Py_CLEAR(self->kw);
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Py_CLEAR(self->dict);
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return 0;
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}
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static void
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local_dealloc(localobject *self)
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{
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PyThreadState *tstate;
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if (self->key
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&& (tstate = PyThreadState_Get())
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&& tstate->interp) {
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for(tstate = PyInterpreterState_ThreadHead(tstate->interp);
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tstate;
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tstate = PyThreadState_Next(tstate)
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)
|
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if (tstate->dict &&
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PyDict_GetItem(tstate->dict, self->key))
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PyDict_DelItem(tstate->dict, self->key);
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}
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local_clear(self);
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self->ob_type->tp_free((PyObject*)self);
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}
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static PyObject *
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_ldict(localobject *self)
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{
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PyObject *tdict, *ldict;
|
||||
|
||||
tdict = PyThreadState_GetDict();
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if (tdict == NULL) {
|
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PyErr_SetString(PyExc_SystemError,
|
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"Couldn't get thread-state dictionary");
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return NULL;
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}
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|
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ldict = PyDict_GetItem(tdict, self->key);
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if (ldict == NULL) {
|
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ldict = PyDict_New(); /* we own ldict */
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|
||||
if (ldict == NULL)
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return NULL;
|
||||
else {
|
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int i = PyDict_SetItem(tdict, self->key, ldict);
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Py_DECREF(ldict); /* now ldict is borowed */
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if (i < 0)
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return NULL;
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}
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Py_CLEAR(self->dict);
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Py_INCREF(ldict);
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self->dict = ldict; /* still borrowed */
|
||||
|
||||
if (self->ob_type->tp_init != PyBaseObject_Type.tp_init &&
|
||||
self->ob_type->tp_init((PyObject*)self,
|
||||
self->args, self->kw) < 0
|
||||
) {
|
||||
/* we need to get rid of ldict from thread so
|
||||
we create a new one the next time we do an attr
|
||||
acces */
|
||||
PyDict_DelItem(tdict, self->key);
|
||||
return NULL;
|
||||
}
|
||||
|
||||
}
|
||||
else if (self->dict != ldict) {
|
||||
Py_CLEAR(self->dict);
|
||||
Py_INCREF(ldict);
|
||||
self->dict = ldict;
|
||||
}
|
||||
|
||||
return ldict;
|
||||
}
|
||||
|
||||
static PyObject *
|
||||
local_getattro(localobject *self, PyObject *name)
|
||||
{
|
||||
PyObject *ldict, *value;
|
||||
|
||||
ldict = _ldict(self);
|
||||
if (ldict == NULL)
|
||||
return NULL;
|
||||
|
||||
if (self->ob_type != &localtype)
|
||||
/* use generic lookup for subtypes */
|
||||
return PyObject_GenericGetAttr((PyObject *)self, name);
|
||||
|
||||
/* Optimization: just look in dict ourselves */
|
||||
value = PyDict_GetItem(ldict, name);
|
||||
if (value == NULL)
|
||||
/* Fall back on generic to get __class__ and __dict__ */
|
||||
return PyObject_GenericGetAttr((PyObject *)self, name);
|
||||
|
||||
Py_INCREF(value);
|
||||
return value;
|
||||
}
|
||||
|
||||
static int
|
||||
local_setattro(localobject *self, PyObject *name, PyObject *v)
|
||||
{
|
||||
PyObject *ldict;
|
||||
|
||||
ldict = _ldict(self);
|
||||
if (ldict == NULL)
|
||||
return -1;
|
||||
|
||||
return PyObject_GenericSetAttr((PyObject *)self, name, v);
|
||||
}
|
||||
|
||||
static PyObject *
|
||||
local_getdict(localobject *self, void *closure)
|
||||
{
|
||||
if (self->dict == NULL) {
|
||||
PyErr_SetString(PyExc_AttributeError, "__dict__");
|
||||
return NULL;
|
||||
}
|
||||
|
||||
Py_INCREF(self->dict);
|
||||
return self->dict;
|
||||
}
|
||||
|
||||
static PyGetSetDef local_getset[] = {
|
||||
{"__dict__",
|
||||
(getter)local_getdict, (setter)0,
|
||||
"Local-data dictionary",
|
||||
NULL},
|
||||
{NULL} /* Sentinel */
|
||||
};
|
||||
|
||||
static PyTypeObject localtype = {
|
||||
PyObject_HEAD_INIT(NULL)
|
||||
/* ob_size */ 0,
|
||||
/* tp_name */ "thread._local",
|
||||
/* tp_basicsize */ sizeof(localobject),
|
||||
/* tp_itemsize */ 0,
|
||||
/* tp_dealloc */ (destructor)local_dealloc,
|
||||
/* tp_print */ (printfunc)0,
|
||||
/* tp_getattr */ (getattrfunc)0,
|
||||
/* tp_setattr */ (setattrfunc)0,
|
||||
/* tp_compare */ (cmpfunc)0,
|
||||
/* tp_repr */ (reprfunc)0,
|
||||
/* tp_as_number */ 0,
|
||||
/* tp_as_sequence */ 0,
|
||||
/* tp_as_mapping */ 0,
|
||||
/* tp_hash */ (hashfunc)0,
|
||||
/* tp_call */ (ternaryfunc)0,
|
||||
/* tp_str */ (reprfunc)0,
|
||||
/* tp_getattro */ (getattrofunc)local_getattro,
|
||||
/* tp_setattro */ (setattrofunc)local_setattro,
|
||||
/* tp_as_buffer */ 0,
|
||||
/* tp_flags */ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
|
||||
/* tp_doc */ "Thread-local data",
|
||||
/* tp_traverse */ (traverseproc)local_traverse,
|
||||
/* tp_clear */ (inquiry)local_clear,
|
||||
/* tp_richcompare */ (richcmpfunc)0,
|
||||
/* tp_weaklistoffset */ (long)0,
|
||||
/* tp_iter */ (getiterfunc)0,
|
||||
/* tp_iternext */ (iternextfunc)0,
|
||||
/* tp_methods */ 0,
|
||||
/* tp_members */ 0,
|
||||
/* tp_getset */ local_getset,
|
||||
/* tp_base */ 0,
|
||||
/* tp_dict */ 0, /* internal use */
|
||||
/* tp_descr_get */ (descrgetfunc)0,
|
||||
/* tp_descr_set */ (descrsetfunc)0,
|
||||
/* tp_dictoffset */ offsetof(localobject, dict),
|
||||
/* tp_init */ (initproc)0,
|
||||
/* tp_alloc */ (allocfunc)0,
|
||||
/* tp_new */ (newfunc)local_new,
|
||||
/* tp_free */ 0, /* Low-level free-mem routine */
|
||||
/* tp_is_gc */ (inquiry)0, /* For PyObject_IS_GC */
|
||||
};
|
||||
|
||||
|
||||
/* Module functions */
|
||||
|
||||
|
|
@ -389,6 +642,10 @@ PyMODINIT_FUNC
|
|||
initthread(void)
|
||||
{
|
||||
PyObject *m, *d;
|
||||
|
||||
/* Initialize types: */
|
||||
if (PyType_Ready(&localtype) < 0)
|
||||
return;
|
||||
|
||||
/* Create the module and add the functions */
|
||||
m = Py_InitModule3("thread", thread_methods, thread_doc);
|
||||
|
|
@ -401,6 +658,9 @@ initthread(void)
|
|||
Py_INCREF(&Locktype);
|
||||
PyDict_SetItemString(d, "LockType", (PyObject *)&Locktype);
|
||||
|
||||
if (PyModule_AddObject(m, "_local", (PyObject *)&localtype) < 0)
|
||||
return;
|
||||
|
||||
/* Initialize the C thread library */
|
||||
PyThread_init_thread();
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue