:right-sidebar: True ThreadPool =================================================================== .. currentmodule:: gi.repository.GLib .. class:: ThreadPool(*args, **kwargs) :no-contents-entry: The ``GThreadPool`` struct represents a thread pool. A thread pool is useful when you wish to asynchronously fork out the execution of work and continue working in your own thread. If that will happen often, the overhead of starting and destroying a thread each time might be too high. In such cases reusing already started threads seems like a good idea. And it indeed is, but implementing this can be tedious and error-prone. Therefore GLib provides thread pools for your convenience. An added advantage is, that the threads can be shared between the different subsystems of your program, when they are using GLib. To create a new thread pool, you use :obj:`~gi.repository.GLib.ThreadPool.new`\. It is destroyed by :obj:`~gi.repository.GLib.ThreadPool.free`\. If you want to execute a certain task within a thread pool, use :obj:`~gi.repository.GLib.ThreadPool.push`\. To get the current number of running threads you call :obj:`~gi.repository.GLib.ThreadPool.get_num_threads`\. To get the number of still unprocessed tasks you call :obj:`~gi.repository.GLib.ThreadPool.unprocessed`\. To control the maximum number of threads for a thread pool, you use :obj:`~gi.repository.GLib.ThreadPool.get_max_threads`\. and :obj:`~gi.repository.GLib.ThreadPool.set_max_threads`\. Finally you can control the number of unused threads, that are kept alive by GLib for future use. The current number can be fetched with :obj:`~gi.repository.GLib.ThreadPool.get_num_unused_threads`\. The maximum number can be controlled by :obj:`~gi.repository.GLib.ThreadPool.get_max_unused_threads` and :obj:`~gi.repository.GLib.ThreadPool.set_max_unused_threads`\. All currently unused threads can be stopped by calling :obj:`~gi.repository.GLib.ThreadPool.stop_unused_threads`\. Methods ------- .. rst-class:: interim-class .. class:: ThreadPool :no-index: .. method:: free(immediate: bool, wait_: bool) -> None Frees all resources allocated for ``pool``\. If ``immediate`` is :const:`True`, no new task is processed for ``pool``\. Otherwise ``pool`` is not freed before the last task is processed. Note however, that no thread of this pool is interrupted while processing a task. Instead at least all still running threads can finish their tasks before the ``pool`` is freed. If ``wait_`` is :const:`True`, this function does not return before all tasks to be processed (dependent on ``immediate``\, whether all or only the currently running) are ready. Otherwise this function returns immediately. After calling this function ``pool`` must not be used anymore. :param immediate: should ``pool`` shut down immediately? :param wait_: should the function wait for all tasks to be finished? .. classmethod:: get_max_idle_time() -> int This function will return the maximum ``interval`` that a thread will wait in the thread pool for new tasks before being stopped. If this function returns 0, threads waiting in the thread pool for new work are not stopped. .. versionadded:: 2.10 .. method:: get_max_threads() -> int Returns the maximal number of threads for ``pool``\. .. classmethod:: get_max_unused_threads() -> int Returns the maximal allowed number of unused threads. .. method:: get_num_threads() -> int Returns the number of threads currently running in ``pool``\. .. classmethod:: get_num_unused_threads() -> int Returns the number of currently unused threads. .. method:: move_to_front(data: ~typing.Any = None) -> bool Moves the item to the front of the queue of unprocessed items, so that it will be processed next. .. versionadded:: 2.46 :param data: an unprocessed item in the pool .. method:: push(data: ~typing.Any = None) -> bool Inserts ``data`` into the list of tasks to be executed by ``pool``\. When the number of currently running threads is lower than the maximal allowed number of threads, a new thread is started (or reused) with the properties given to :func:`~gi.repository.GLib.ThreadPool.new`. Otherwise, ``data`` stays in the queue until a thread in this pool finishes its previous task and processes ``data``\. ``error`` can be :const:`None` to ignore errors, or non-:const:`None` to report errors. An error can only occur when a new thread couldn't be created. In that case ``data`` is simply appended to the queue of work to do. Before version 2.32, this function did not return a success status. :param data: a new task for ``pool`` .. classmethod:: set_max_idle_time() -> None This function will set the maximum ``interval`` that a thread waiting in the pool for new tasks can be idle for before being stopped. This function is similar to calling :func:`~gi.repository.GLib.ThreadPool.stop_unused_threads` on a regular timeout, except this is done on a per thread basis. By setting ``interval`` to 0, idle threads will not be stopped. The default value is 15000 (15 seconds). .. versionadded:: 2.10 .. method:: set_max_threads(max_threads: int) -> bool Sets the maximal allowed number of threads for ``pool``\. A value of -1 means that the maximal number of threads is unlimited. If ``pool`` is an exclusive thread pool, setting the maximal number of threads to -1 is not allowed. Setting ``max_threads`` to 0 means stopping all work for ``pool``\. It is effectively frozen until ``max_threads`` is set to a non-zero value again. A thread is never terminated while calling ``func``\, as supplied by :func:`~gi.repository.GLib.ThreadPool.new`. Instead the maximal number of threads only has effect for the allocation of new threads in :func:`~gi.repository.GLib.ThreadPool.push`. A new thread is allocated, whenever the number of currently running threads in ``pool`` is smaller than the maximal number. ``error`` can be :const:`None` to ignore errors, or non-:const:`None` to report errors. An error can only occur when a new thread couldn't be created. Before version 2.32, this function did not return a success status. :param max_threads: a new maximal number of threads for ``pool``\, or -1 for unlimited .. classmethod:: set_max_unused_threads() -> None Sets the maximal number of unused threads to ``max_threads``\. If ``max_threads`` is -1, no limit is imposed on the number of unused threads. The default value is 2. .. classmethod:: stop_unused_threads() -> None Stops all currently unused threads. This does not change the maximal number of unused threads. This function can be used to regularly stop all unused threads e.g. from :func:`~gi.repository.GLib.timeout_add`. .. method:: unprocessed() -> int Returns the number of tasks still unprocessed in ``pool``\. Fields ------ .. rst-class:: interim-class .. class:: ThreadPool :no-index: .. attribute:: exclusive Are all threads exclusive to this pool .. attribute:: func The function to execute in the threads of this pool .. attribute:: user_data The user data for the threads of this pool