mirror of https://github.com/python/cpython
715 lines
28 KiB
ReStructuredText
715 lines
28 KiB
ReStructuredText
:mod:`!concurrent.futures` --- Launching parallel tasks
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=======================================================
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.. module:: concurrent.futures
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:synopsis: Execute computations concurrently using threads or processes.
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.. versionadded:: 3.2
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**Source code:** :source:`Lib/concurrent/futures/thread.py`
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and :source:`Lib/concurrent/futures/process.py`
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--------------
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The :mod:`concurrent.futures` module provides a high-level interface for
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asynchronously executing callables.
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The asynchronous execution can be performed with threads, using
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:class:`ThreadPoolExecutor` or :class:`InterpreterPoolExecutor`,
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or separate processes, using :class:`ProcessPoolExecutor`.
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Each implements the same interface, which is defined
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by the abstract :class:`Executor` class.
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.. include:: ../includes/wasm-notavail.rst
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Executor Objects
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----------------
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.. class:: Executor
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An abstract class that provides methods to execute calls asynchronously. It
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should not be used directly, but through its concrete subclasses.
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.. method:: submit(fn, /, *args, **kwargs)
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Schedules the callable, *fn*, to be executed as ``fn(*args, **kwargs)``
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and returns a :class:`Future` object representing the execution of the
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callable. ::
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with ThreadPoolExecutor(max_workers=1) as executor:
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future = executor.submit(pow, 323, 1235)
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print(future.result())
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.. method:: map(fn, *iterables, timeout=None, chunksize=1)
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Similar to :func:`map(fn, *iterables) <map>` except:
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* the *iterables* are collected immediately rather than lazily;
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* *fn* is executed asynchronously and several calls to
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*fn* may be made concurrently.
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The returned iterator raises a :exc:`TimeoutError`
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if :meth:`~iterator.__next__` is called and the result isn't available
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after *timeout* seconds from the original call to :meth:`Executor.map`.
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*timeout* can be an int or a float. If *timeout* is not specified or
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``None``, there is no limit to the wait time.
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If a *fn* call raises an exception, then that exception will be
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raised when its value is retrieved from the iterator.
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When using :class:`ProcessPoolExecutor`, this method chops *iterables*
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into a number of chunks which it submits to the pool as separate
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tasks. The (approximate) size of these chunks can be specified by
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setting *chunksize* to a positive integer. For very long iterables,
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using a large value for *chunksize* can significantly improve
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performance compared to the default size of 1. With
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:class:`ThreadPoolExecutor` and :class:`InterpreterPoolExecutor`,
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*chunksize* has no effect.
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.. versionchanged:: 3.5
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Added the *chunksize* argument.
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.. method:: shutdown(wait=True, *, cancel_futures=False)
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Signal the executor that it should free any resources that it is using
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when the currently pending futures are done executing. Calls to
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:meth:`Executor.submit` and :meth:`Executor.map` made after shutdown will
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raise :exc:`RuntimeError`.
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If *wait* is ``True`` then this method will not return until all the
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pending futures are done executing and the resources associated with the
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executor have been freed. If *wait* is ``False`` then this method will
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return immediately and the resources associated with the executor will be
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freed when all pending futures are done executing. Regardless of the
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value of *wait*, the entire Python program will not exit until all
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pending futures are done executing.
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If *cancel_futures* is ``True``, this method will cancel all pending
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futures that the executor has not started running. Any futures that
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are completed or running won't be cancelled, regardless of the value
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of *cancel_futures*.
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If both *cancel_futures* and *wait* are ``True``, all futures that the
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executor has started running will be completed prior to this method
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returning. The remaining futures are cancelled.
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You can avoid having to call this method explicitly if you use the
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:keyword:`with` statement, which will shutdown the :class:`Executor`
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(waiting as if :meth:`Executor.shutdown` were called with *wait* set to
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``True``)::
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import shutil
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with ThreadPoolExecutor(max_workers=4) as e:
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e.submit(shutil.copy, 'src1.txt', 'dest1.txt')
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e.submit(shutil.copy, 'src2.txt', 'dest2.txt')
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e.submit(shutil.copy, 'src3.txt', 'dest3.txt')
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e.submit(shutil.copy, 'src4.txt', 'dest4.txt')
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.. versionchanged:: 3.9
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Added *cancel_futures*.
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ThreadPoolExecutor
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------------------
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:class:`ThreadPoolExecutor` is an :class:`Executor` subclass that uses a pool of
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threads to execute calls asynchronously.
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Deadlocks can occur when the callable associated with a :class:`Future` waits on
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the results of another :class:`Future`. For example::
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import time
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def wait_on_b():
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time.sleep(5)
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print(b.result()) # b will never complete because it is waiting on a.
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return 5
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def wait_on_a():
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time.sleep(5)
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print(a.result()) # a will never complete because it is waiting on b.
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return 6
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executor = ThreadPoolExecutor(max_workers=2)
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a = executor.submit(wait_on_b)
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b = executor.submit(wait_on_a)
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And::
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def wait_on_future():
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f = executor.submit(pow, 5, 2)
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# This will never complete because there is only one worker thread and
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# it is executing this function.
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print(f.result())
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executor = ThreadPoolExecutor(max_workers=1)
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executor.submit(wait_on_future)
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.. class:: ThreadPoolExecutor(max_workers=None, thread_name_prefix='', initializer=None, initargs=())
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An :class:`Executor` subclass that uses a pool of at most *max_workers*
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threads to execute calls asynchronously.
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All threads enqueued to ``ThreadPoolExecutor`` will be joined before the
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interpreter can exit. Note that the exit handler which does this is
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executed *before* any exit handlers added using ``atexit``. This means
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exceptions in the main thread must be caught and handled in order to
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signal threads to exit gracefully. For this reason, it is recommended
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that ``ThreadPoolExecutor`` not be used for long-running tasks.
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*initializer* is an optional callable that is called at the start of
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each worker thread; *initargs* is a tuple of arguments passed to the
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initializer. Should *initializer* raise an exception, all currently
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pending jobs will raise a :exc:`~concurrent.futures.thread.BrokenThreadPool`,
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as well as any attempt to submit more jobs to the pool.
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.. versionchanged:: 3.5
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If *max_workers* is ``None`` or
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not given, it will default to the number of processors on the machine,
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multiplied by ``5``, assuming that :class:`ThreadPoolExecutor` is often
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used to overlap I/O instead of CPU work and the number of workers
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should be higher than the number of workers
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for :class:`ProcessPoolExecutor`.
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.. versionchanged:: 3.6
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Added the *thread_name_prefix* parameter to allow users to
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control the :class:`threading.Thread` names for worker threads created by
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the pool for easier debugging.
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.. versionchanged:: 3.7
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Added the *initializer* and *initargs* arguments.
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.. versionchanged:: 3.8
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Default value of *max_workers* is changed to ``min(32, os.cpu_count() + 4)``.
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This default value preserves at least 5 workers for I/O bound tasks.
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It utilizes at most 32 CPU cores for CPU bound tasks which release the GIL.
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And it avoids using very large resources implicitly on many-core machines.
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ThreadPoolExecutor now reuses idle worker threads before starting
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*max_workers* worker threads too.
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.. versionchanged:: 3.13
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Default value of *max_workers* is changed to
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``min(32, (os.process_cpu_count() or 1) + 4)``.
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.. _threadpoolexecutor-example:
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ThreadPoolExecutor Example
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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::
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import concurrent.futures
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import urllib.request
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URLS = ['http://www.foxnews.com/',
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'http://www.cnn.com/',
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'http://europe.wsj.com/',
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'http://www.bbc.co.uk/',
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'http://nonexistant-subdomain.python.org/']
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# Retrieve a single page and report the URL and contents
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def load_url(url, timeout):
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with urllib.request.urlopen(url, timeout=timeout) as conn:
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return conn.read()
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# We can use a with statement to ensure threads are cleaned up promptly
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with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
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# Start the load operations and mark each future with its URL
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future_to_url = {executor.submit(load_url, url, 60): url for url in URLS}
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for future in concurrent.futures.as_completed(future_to_url):
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url = future_to_url[future]
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try:
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data = future.result()
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except Exception as exc:
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print('%r generated an exception: %s' % (url, exc))
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else:
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print('%r page is %d bytes' % (url, len(data)))
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InterpreterPoolExecutor
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-----------------------
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The :class:`InterpreterPoolExecutor` class uses a pool of interpreters
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to execute calls asynchronously. It is a :class:`ThreadPoolExecutor`
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subclass, which means each worker is running in its own thread.
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The difference here is that each worker has its own interpreter,
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and runs each task using that interpreter.
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The biggest benefit to using interpreters instead of only threads
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is true multi-core parallelism. Each interpreter has its own
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:term:`Global Interpreter Lock <global interpreter lock>`, so code
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running in one interpreter can run on one CPU core, while code in
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another interpreter runs unblocked on a different core.
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The tradeoff is that writing concurrent code for use with multiple
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interpreters can take extra effort. However, this is because it
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forces you to be deliberate about how and when interpreters interact,
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and to be explicit about what data is shared between interpreters.
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This results in several benefits that help balance the extra effort,
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including true multi-core parallelism, For example, code written
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this way can make it easier to reason about concurrency. Another
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major benefit is that you don't have to deal with several of the
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big pain points of using threads, like nrace conditions.
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Each worker's interpreter is isolated from all the other interpreters.
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"Isolated" means each interpreter has its own runtime state and
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operates completely independently. For example, if you redirect
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:data:`sys.stdout` in one interpreter, it will not be automatically
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redirected any other interpreter. If you import a module in one
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interpreter, it is not automatically imported in any other. You
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would need to import the module separately in interpreter where
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you need it. In fact, each module imported in an interpreter is
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a completely separate object from the same module in a different
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interpreter, including :mod:`sys`, :mod:`builtins`,
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and even ``__main__``.
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Isolation means a mutable object, or other data, cannot be used
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by more than one interpreter at the same time. That effectively means
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interpreters cannot actually share such objects or data. Instead,
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each interpreter must have its own copy, and you will have to
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synchronize any changes between the copies manually. Immutable
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objects and data, like the builtin singletons, strings, and tuples
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of immutable objects, don't have these limitations.
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Communicating and synchronizing between interpreters is most effectively
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done using dedicated tools, like those proposed in :pep:`734`. One less
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efficient alternative is to serialize with :mod:`pickle` and then send
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the bytes over a shared :mod:`socket <socket>` or
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:func:`pipe <os.pipe>`.
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.. class:: InterpreterPoolExecutor(max_workers=None, thread_name_prefix='', initializer=None, initargs=(), shared=None)
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A :class:`ThreadPoolExecutor` subclass that executes calls asynchronously
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using a pool of at most *max_workers* threads. Each thread runs
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tasks in its own interpreter. The worker interpreters are isolated
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from each other, which means each has its own runtime state and that
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they can't share any mutable objects or other data. Each interpreter
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has its own :term:`Global Interpreter Lock <global interpreter lock>`,
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which means code run with this executor has true multi-core parallelism.
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The optional *initializer* and *initargs* arguments have the same
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meaning as for :class:`!ThreadPoolExecutor`: the initializer is run
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when each worker is created, though in this case it is run.in
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the worker's interpreter. The executor serializes the *initializer*
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and *initargs* using :mod:`pickle` when sending them to the worker's
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interpreter.
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.. note::
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Functions defined in the ``__main__`` module cannot be pickled
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and thus cannot be used.
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.. note::
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The executor may replace uncaught exceptions from *initializer*
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with :class:`~concurrent.futures.interpreter.ExecutionFailed`.
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The optional *shared* argument is a :class:`dict` of objects that all
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interpreters in the pool share. The *shared* items are added to each
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interpreter's ``__main__`` module. Not all objects are shareable.
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Shareable objects include the builtin singletons, :class:`str`
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and :class:`bytes`, and :class:`memoryview`. See :pep:`734`
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for more info.
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Other caveats from parent :class:`ThreadPoolExecutor` apply here.
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:meth:`~Executor.submit` and :meth:`~Executor.map` work like normal,
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except the worker serializes the callable and arguments using
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:mod:`pickle` when sending them to its interpreter. The worker
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likewise serializes the return value when sending it back.
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.. note::
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Functions defined in the ``__main__`` module cannot be pickled
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and thus cannot be used.
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When a worker's current task raises an uncaught exception, the worker
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always tries to preserve the exception as-is. If that is successful
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then it also sets the ``__cause__`` to a corresponding
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:class:`~concurrent.futures.interpreter.ExecutionFailed`
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instance, which contains a summary of the original exception.
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In the uncommon case that the worker is not able to preserve the
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original as-is then it directly preserves the corresponding
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:class:`~concurrent.futures.interpreter.ExecutionFailed`
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instance instead.
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ProcessPoolExecutor
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-------------------
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The :class:`ProcessPoolExecutor` class is an :class:`Executor` subclass that
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uses a pool of processes to execute calls asynchronously.
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:class:`ProcessPoolExecutor` uses the :mod:`multiprocessing` module, which
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allows it to side-step the :term:`Global Interpreter Lock
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<global interpreter lock>` but also means that
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only picklable objects can be executed and returned.
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The ``__main__`` module must be importable by worker subprocesses. This means
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that :class:`ProcessPoolExecutor` will not work in the interactive interpreter.
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Calling :class:`Executor` or :class:`Future` methods from a callable submitted
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to a :class:`ProcessPoolExecutor` will result in deadlock.
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.. class:: ProcessPoolExecutor(max_workers=None, mp_context=None, initializer=None, initargs=(), max_tasks_per_child=None)
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An :class:`Executor` subclass that executes calls asynchronously using a pool
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of at most *max_workers* processes. If *max_workers* is ``None`` or not
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given, it will default to :func:`os.process_cpu_count`.
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If *max_workers* is less than or equal to ``0``, then a :exc:`ValueError`
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will be raised.
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On Windows, *max_workers* must be less than or equal to ``61``. If it is not
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then :exc:`ValueError` will be raised. If *max_workers* is ``None``, then
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the default chosen will be at most ``61``, even if more processors are
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available.
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*mp_context* can be a :mod:`multiprocessing` context or ``None``. It will be
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used to launch the workers. If *mp_context* is ``None`` or not given, the
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default :mod:`multiprocessing` context is used.
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See :ref:`multiprocessing-start-methods`.
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*initializer* is an optional callable that is called at the start of
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each worker process; *initargs* is a tuple of arguments passed to the
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initializer. Should *initializer* raise an exception, all currently
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pending jobs will raise a :exc:`~concurrent.futures.process.BrokenProcessPool`,
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as well as any attempt to submit more jobs to the pool.
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*max_tasks_per_child* is an optional argument that specifies the maximum
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number of tasks a single process can execute before it will exit and be
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replaced with a fresh worker process. By default *max_tasks_per_child* is
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``None`` which means worker processes will live as long as the pool. When
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a max is specified, the "spawn" multiprocessing start method will be used by
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default in absence of a *mp_context* parameter. This feature is incompatible
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with the "fork" start method.
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.. versionchanged:: 3.3
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When one of the worker processes terminates abruptly, a
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:exc:`~concurrent.futures.process.BrokenProcessPool` error is now raised.
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Previously, behaviour
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was undefined but operations on the executor or its futures would often
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freeze or deadlock.
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.. versionchanged:: 3.7
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The *mp_context* argument was added to allow users to control the
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start_method for worker processes created by the pool.
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Added the *initializer* and *initargs* arguments.
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.. versionchanged:: 3.11
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The *max_tasks_per_child* argument was added to allow users to
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control the lifetime of workers in the pool.
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.. versionchanged:: 3.12
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On POSIX systems, if your application has multiple threads and the
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:mod:`multiprocessing` context uses the ``"fork"`` start method:
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The :func:`os.fork` function called internally to spawn workers may raise a
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:exc:`DeprecationWarning`. Pass a *mp_context* configured to use a
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different start method. See the :func:`os.fork` documentation for
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further explanation.
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.. versionchanged:: 3.13
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*max_workers* uses :func:`os.process_cpu_count` by default, instead of
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:func:`os.cpu_count`.
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.. versionchanged:: 3.14
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The default process start method (see
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:ref:`multiprocessing-start-methods`) changed away from *fork*. If you
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require the *fork* start method for :class:`ProcessPoolExecutor` you must
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explicitly pass ``mp_context=multiprocessing.get_context("fork")``.
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.. _processpoolexecutor-example:
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ProcessPoolExecutor Example
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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::
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import concurrent.futures
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import math
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PRIMES = [
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112272535095293,
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112582705942171,
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112272535095293,
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115280095190773,
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115797848077099,
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1099726899285419]
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def is_prime(n):
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if n < 2:
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return False
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if n == 2:
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return True
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if n % 2 == 0:
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return False
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sqrt_n = int(math.floor(math.sqrt(n)))
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for i in range(3, sqrt_n + 1, 2):
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if n % i == 0:
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return False
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return True
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def main():
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with concurrent.futures.ProcessPoolExecutor() as executor:
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for number, prime in zip(PRIMES, executor.map(is_prime, PRIMES)):
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print('%d is prime: %s' % (number, prime))
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if __name__ == '__main__':
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main()
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Future Objects
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--------------
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The :class:`Future` class encapsulates the asynchronous execution of a callable.
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:class:`Future` instances are created by :meth:`Executor.submit`.
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.. class:: Future
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Encapsulates the asynchronous execution of a callable. :class:`Future`
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instances are created by :meth:`Executor.submit` and should not be created
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directly except for testing.
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.. method:: cancel()
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Attempt to cancel the call. If the call is currently being executed or
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finished running and cannot be cancelled then the method will return
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``False``, otherwise the call will be cancelled and the method will
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return ``True``.
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.. method:: cancelled()
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Return ``True`` if the call was successfully cancelled.
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|
.. method:: running()
|
|
|
|
Return ``True`` if the call is currently being executed and cannot be
|
|
cancelled.
|
|
|
|
.. method:: done()
|
|
|
|
Return ``True`` if the call was successfully cancelled or finished
|
|
running.
|
|
|
|
.. method:: result(timeout=None)
|
|
|
|
Return the value returned by the call. If the call hasn't yet completed
|
|
then this method will wait up to *timeout* seconds. If the call hasn't
|
|
completed in *timeout* seconds, then a
|
|
:exc:`TimeoutError` will be raised. *timeout* can be
|
|
an int or float. If *timeout* is not specified or ``None``, there is no
|
|
limit to the wait time.
|
|
|
|
If the future is cancelled before completing then :exc:`.CancelledError`
|
|
will be raised.
|
|
|
|
If the call raised an exception, this method will raise the same exception.
|
|
|
|
.. method:: exception(timeout=None)
|
|
|
|
Return the exception raised by the call. If the call hasn't yet
|
|
completed then this method will wait up to *timeout* seconds. If the
|
|
call hasn't completed in *timeout* seconds, then a
|
|
:exc:`TimeoutError` will be raised. *timeout* can be
|
|
an int or float. If *timeout* is not specified or ``None``, there is no
|
|
limit to the wait time.
|
|
|
|
If the future is cancelled before completing then :exc:`.CancelledError`
|
|
will be raised.
|
|
|
|
If the call completed without raising, ``None`` is returned.
|
|
|
|
.. method:: add_done_callback(fn)
|
|
|
|
Attaches the callable *fn* to the future. *fn* will be called, with the
|
|
future as its only argument, when the future is cancelled or finishes
|
|
running.
|
|
|
|
Added callables are called in the order that they were added and are
|
|
always called in a thread belonging to the process that added them. If
|
|
the callable raises an :exc:`Exception` subclass, it will be logged and
|
|
ignored. If the callable raises a :exc:`BaseException` subclass, the
|
|
behavior is undefined.
|
|
|
|
If the future has already completed or been cancelled, *fn* will be
|
|
called immediately.
|
|
|
|
The following :class:`Future` methods are meant for use in unit tests and
|
|
:class:`Executor` implementations.
|
|
|
|
.. method:: set_running_or_notify_cancel()
|
|
|
|
This method should only be called by :class:`Executor` implementations
|
|
before executing the work associated with the :class:`Future` and by unit
|
|
tests.
|
|
|
|
If the method returns ``False`` then the :class:`Future` was cancelled,
|
|
i.e. :meth:`Future.cancel` was called and returned ``True``. Any threads
|
|
waiting on the :class:`Future` completing (i.e. through
|
|
:func:`as_completed` or :func:`wait`) will be woken up.
|
|
|
|
If the method returns ``True`` then the :class:`Future` was not cancelled
|
|
and has been put in the running state, i.e. calls to
|
|
:meth:`Future.running` will return ``True``.
|
|
|
|
This method can only be called once and cannot be called after
|
|
:meth:`Future.set_result` or :meth:`Future.set_exception` have been
|
|
called.
|
|
|
|
.. method:: set_result(result)
|
|
|
|
Sets the result of the work associated with the :class:`Future` to
|
|
*result*.
|
|
|
|
This method should only be used by :class:`Executor` implementations and
|
|
unit tests.
|
|
|
|
.. versionchanged:: 3.8
|
|
This method raises
|
|
:exc:`concurrent.futures.InvalidStateError` if the :class:`Future` is
|
|
already done.
|
|
|
|
.. method:: set_exception(exception)
|
|
|
|
Sets the result of the work associated with the :class:`Future` to the
|
|
:class:`Exception` *exception*.
|
|
|
|
This method should only be used by :class:`Executor` implementations and
|
|
unit tests.
|
|
|
|
.. versionchanged:: 3.8
|
|
This method raises
|
|
:exc:`concurrent.futures.InvalidStateError` if the :class:`Future` is
|
|
already done.
|
|
|
|
Module Functions
|
|
----------------
|
|
|
|
.. function:: wait(fs, timeout=None, return_when=ALL_COMPLETED)
|
|
|
|
Wait for the :class:`Future` instances (possibly created by different
|
|
:class:`Executor` instances) given by *fs* to complete. Duplicate futures
|
|
given to *fs* are removed and will be returned only once. Returns a named
|
|
2-tuple of sets. The first set, named ``done``, contains the futures that
|
|
completed (finished or cancelled futures) before the wait completed. The
|
|
second set, named ``not_done``, contains the futures that did not complete
|
|
(pending or running futures).
|
|
|
|
*timeout* can be used to control the maximum number of seconds to wait before
|
|
returning. *timeout* can be an int or float. If *timeout* is not specified
|
|
or ``None``, there is no limit to the wait time.
|
|
|
|
*return_when* indicates when this function should return. It must be one of
|
|
the following constants:
|
|
|
|
.. list-table::
|
|
:header-rows: 1
|
|
|
|
* - Constant
|
|
- Description
|
|
|
|
* - .. data:: FIRST_COMPLETED
|
|
- The function will return when any future finishes or is cancelled.
|
|
|
|
* - .. data:: FIRST_EXCEPTION
|
|
- The function will return when any future finishes by raising an
|
|
exception. If no future raises an exception
|
|
then it is equivalent to :const:`ALL_COMPLETED`.
|
|
|
|
* - .. data:: ALL_COMPLETED
|
|
- The function will return when all futures finish or are cancelled.
|
|
|
|
.. function:: as_completed(fs, timeout=None)
|
|
|
|
Returns an iterator over the :class:`Future` instances (possibly created by
|
|
different :class:`Executor` instances) given by *fs* that yields futures as
|
|
they complete (finished or cancelled futures). Any futures given by *fs* that
|
|
are duplicated will be returned once. Any futures that completed before
|
|
:func:`as_completed` is called will be yielded first. The returned iterator
|
|
raises a :exc:`TimeoutError` if :meth:`~iterator.__next__`
|
|
is called and the result isn't available after *timeout* seconds from the
|
|
original call to :func:`as_completed`. *timeout* can be an int or float. If
|
|
*timeout* is not specified or ``None``, there is no limit to the wait time.
|
|
|
|
|
|
.. seealso::
|
|
|
|
:pep:`3148` -- futures - execute computations asynchronously
|
|
The proposal which described this feature for inclusion in the Python
|
|
standard library.
|
|
|
|
|
|
Exception classes
|
|
-----------------
|
|
|
|
.. currentmodule:: concurrent.futures
|
|
|
|
.. exception:: CancelledError
|
|
|
|
Raised when a future is cancelled.
|
|
|
|
.. exception:: TimeoutError
|
|
|
|
A deprecated alias of :exc:`TimeoutError`,
|
|
raised when a future operation exceeds the given timeout.
|
|
|
|
.. versionchanged:: 3.11
|
|
|
|
This class was made an alias of :exc:`TimeoutError`.
|
|
|
|
|
|
.. exception:: BrokenExecutor
|
|
|
|
Derived from :exc:`RuntimeError`, this exception class is raised
|
|
when an executor is broken for some reason, and cannot be used
|
|
to submit or execute new tasks.
|
|
|
|
.. versionadded:: 3.7
|
|
|
|
.. exception:: InvalidStateError
|
|
|
|
Raised when an operation is performed on a future that is not allowed
|
|
in the current state.
|
|
|
|
.. versionadded:: 3.8
|
|
|
|
.. currentmodule:: concurrent.futures.thread
|
|
|
|
.. exception:: BrokenThreadPool
|
|
|
|
Derived from :exc:`~concurrent.futures.BrokenExecutor`, this exception
|
|
class is raised when one of the workers
|
|
of a :class:`~concurrent.futures.ThreadPoolExecutor`
|
|
has failed initializing.
|
|
|
|
.. versionadded:: 3.7
|
|
|
|
.. currentmodule:: concurrent.futures.interpreter
|
|
|
|
.. exception:: BrokenInterpreterPool
|
|
|
|
Derived from :exc:`~concurrent.futures.thread.BrokenThreadPool`,
|
|
this exception class is raised when one of the workers
|
|
of a :class:`~concurrent.futures.InterpreterPoolExecutor`
|
|
has failed initializing.
|
|
|
|
.. versionadded:: next
|
|
|
|
.. exception:: ExecutionFailed
|
|
|
|
Raised from :class:`~concurrent.futures.InterpreterPoolExecutor` when
|
|
the given initializer fails or from
|
|
:meth:`~concurrent.futures.Executor.submit` when there's an uncaught
|
|
exception from the submitted task.
|
|
|
|
.. versionadded:: next
|
|
|
|
.. currentmodule:: concurrent.futures.process
|
|
|
|
.. exception:: BrokenProcessPool
|
|
|
|
Derived from :exc:`~concurrent.futures.BrokenExecutor` (formerly
|
|
:exc:`RuntimeError`), this exception class is raised when one of the
|
|
workers of a :class:`~concurrent.futures.ProcessPoolExecutor`
|
|
has terminated in a non-clean
|
|
fashion (for example, if it was killed from the outside).
|
|
|
|
.. versionadded:: 3.3
|