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Diffstat (limited to 'Lib/_threading_local.py')
-rw-r--r-- | Lib/_threading_local.py | 122 |
1 files changed, 0 insertions, 122 deletions
diff --git a/Lib/_threading_local.py b/Lib/_threading_local.py index b006d76c4e2..0b9e5d3bbf6 100644 --- a/Lib/_threading_local.py +++ b/Lib/_threading_local.py @@ -4,128 +4,6 @@ class. Depending on the version of Python you're using, there may be a faster one available. You should always import the `local` class from `threading`.) - -Thread-local objects support the management of thread-local data. -If you have data that you want to be local to a thread, simply create -a thread-local object and use its attributes: - - >>> mydata = local() - >>> mydata.number = 42 - >>> mydata.number - 42 - -You can also access the local-object's dictionary: - - >>> mydata.__dict__ - {'number': 42} - >>> mydata.__dict__.setdefault('widgets', []) - [] - >>> mydata.widgets - [] - -What's important about thread-local objects is that their data are -local to a thread. If we access the data in a different thread: - - >>> log = [] - >>> def f(): - ... items = sorted(mydata.__dict__.items()) - ... log.append(items) - ... mydata.number = 11 - ... log.append(mydata.number) - - >>> import threading - >>> thread = threading.Thread(target=f) - >>> thread.start() - >>> thread.join() - >>> log - [[], 11] - -we get different data. Furthermore, changes made in the other thread -don't affect data seen in this thread: - - >>> mydata.number - 42 - -Of course, values you get from a local object, including a __dict__ -attribute, are for whatever thread was current at the time the -attribute was read. For that reason, you generally don't want to save -these values across threads, as they apply only to the thread they -came from. - -You can create custom local objects by subclassing the local class: - - >>> class MyLocal(local): - ... number = 2 - ... def __init__(self, /, **kw): - ... self.__dict__.update(kw) - ... def squared(self): - ... return self.number ** 2 - -This can be useful to support default values, methods and -initialization. Note that if you define an __init__ method, it will be -called each time the local object is used in a separate thread. This -is necessary to initialize each thread's dictionary. - -Now if we create a local object: - - >>> mydata = MyLocal(color='red') - -Now we have a default number: - - >>> mydata.number - 2 - -an initial color: - - >>> mydata.color - 'red' - >>> del mydata.color - -And a method that operates on the data: - - >>> mydata.squared() - 4 - -As before, we can access the data in a separate thread: - - >>> log = [] - >>> thread = threading.Thread(target=f) - >>> thread.start() - >>> thread.join() - >>> log - [[('color', 'red')], 11] - -without affecting this thread's data: - - >>> mydata.number - 2 - >>> mydata.color - Traceback (most recent call last): - ... - AttributeError: 'MyLocal' object has no attribute 'color' - -Note that subclasses can define slots, but they are not thread -local. They are shared across threads: - - >>> class MyLocal(local): - ... __slots__ = 'number' - - >>> mydata = MyLocal() - >>> mydata.number = 42 - >>> mydata.color = 'red' - -So, the separate thread: - - >>> thread = threading.Thread(target=f) - >>> thread.start() - >>> thread.join() - -affects what we see: - - >>> mydata.number - 11 - ->>> del mydata """ from weakref import ref |