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Diffstat (limited to 'Doc/library/multiprocessing.rst')
| -rw-r--r-- | Doc/library/multiprocessing.rst | 62 |
1 files changed, 52 insertions, 10 deletions
diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst index 7db2aed..5019eff 100644 --- a/Doc/library/multiprocessing.rst +++ b/Doc/library/multiprocessing.rst @@ -297,7 +297,7 @@ The :mod:`multiprocessing` package mostly replicates the API of the :class:`Process` and exceptions ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -.. class:: Process([group[, target[, name[, args[, kwargs]]]]]) +.. class:: Process([group[, target[, name[, args[, kwargs]]]]], *, daemon=None) Process objects represent activity that is run in a separate process. The :class:`Process` class has equivalents of all the methods of @@ -312,13 +312,19 @@ The :mod:`multiprocessing` package mostly replicates the API of the :sub:`1`,N\ :sub:`2`,...,N\ :sub:`k` is a sequence of integers whose length is determined by the *generation* of the process. *args* is the argument tuple for the target invocation. *kwargs* is a dictionary of keyword - arguments for the target invocation. By default, no arguments are passed to - *target*. + arguments for the target invocation. If provided, the keyword-only *daemon* argument + sets the process :attr:`daemon` flag to ``True`` or ``False``. If ``None`` + (the default), this flag will be inherited from the creating process. + + By default, no arguments are passed to *target*. If a subclass overrides the constructor, it must make sure it invokes the base class constructor (:meth:`Process.__init__`) before doing anything else to the process. + .. versionchanged:: 3.3 + Added the *daemon* argument. + .. method:: run() Method representing the process's activity. @@ -337,10 +343,9 @@ The :mod:`multiprocessing` package mostly replicates the API of the .. method:: join([timeout]) - Block the calling thread until the process whose :meth:`join` method is - called terminates or until the optional timeout occurs. - - If *timeout* is ``None`` then there is no timeout. + If the optional argument *timeout* is ``None`` (the default), the method + blocks until the process whose :meth:`join` method is called terminates. + If *timeout* is a positive number, it blocks at most *timeout* seconds. A process can be joined many times. @@ -405,6 +410,20 @@ The :mod:`multiprocessing` package mostly replicates the API of the See :ref:`multiprocessing-auth-keys`. + .. attribute:: sentinel + + A numeric handle of a system object which will become "ready" when + the process ends. + + On Windows, this is an OS handle usable with the ``WaitForSingleObject`` + and ``WaitForMultipleObjects`` family of API calls. On Unix, this is + a file descriptor usable with primitives from the :mod:`select` module. + + You can use this value if you want to wait on several events at once. + Otherwise calling :meth:`join()` is simpler. + + .. versionadded:: 3.3 + .. method:: terminate() Terminate the process. On Unix this is done using the ``SIGTERM`` signal; @@ -464,7 +483,7 @@ primitives like locks. For passing messages one can use :func:`Pipe` (for a connection between two processes) or a queue (which allows multiple producers and consumers). -The :class:`Queue`, :class:`multiprocessing.queues.SimpleQueue` and :class:`JoinableQueue` types are multi-producer, +The :class:`Queue`, :class:`SimpleQueue` and :class:`JoinableQueue` types are multi-producer, multi-consumer FIFO queues modelled on the :class:`queue.Queue` class in the standard library. They differ in that :class:`Queue` lacks the :meth:`~queue.Queue.task_done` and :meth:`~queue.Queue.join` methods introduced @@ -610,7 +629,7 @@ For an example of the usage of queues for interprocess communication see exits -- see :meth:`join_thread`. -.. class:: multiprocessing.queues.SimpleQueue() +.. class:: SimpleQueue() It is a simplified :class:`Queue` type, very close to a locked :class:`Pipe`. @@ -784,9 +803,14 @@ Connection objects are usually created using :func:`Pipe` -- see also to receive and the other end has closed. If *maxlength* is specified and the message is longer than *maxlength* - then :exc:`IOError` is raised and the connection will no longer be + then :exc:`OSError` is raised and the connection will no longer be readable. + .. versionchanged:: 3.3 + This function used to raise a :exc:`IOError`, which is now an + alias of :exc:`OSError`. + + .. method:: recv_bytes_into(buffer[, offset]) Read into *buffer* a complete message of byte data sent from the other end @@ -1657,6 +1681,24 @@ with the :class:`Pool` class. returned iterator should be considered arbitrary. (Only when there is only one worker process is the order guaranteed to be "correct".) + .. method:: starmap(func, iterable[, chunksize]) + + Like :meth:`map` except that the elements of the `iterable` are expected + to be iterables that are unpacked as arguments. + + Hence an `iterable` of `[(1,2), (3, 4)]` results in `[func(1,2), + func(3,4)]`. + + .. versionadded:: 3.3 + + .. method:: starmap_async(func, iterable[, chunksize[, callback[, error_back]]]) + + A combination of :meth:`starmap` and :meth:`map_async` that iterates over + `iterable` of iterables and calls `func` with the iterables unpacked. + Returns a result object. + + .. versionadded:: 3.3 + .. method:: close() Prevents any more tasks from being submitted to the pool. Once all the |