If the future is cancelled before completing then CancelledError If timeout is not specified or None, there is no Then this method will wait up to timeout seconds. Return True if the call was successfully cancelled or finished Return True if the call is currently being executed and cannot be Return True if the call was successfully cancelled. If the call is currently being executed orįinished running and cannot be cancelled then the method will returnįalse, otherwise the call will be cancelled and the method will Pending jobs will raise a BrokenProcessPool,Īs well as any attempt to submit more jobs to the pool.Īttempt to cancel the call. Should initializer raise an exception, all currently Initializer is an optional callable that is called at the start ofĮach worker process initargs is a tuple of arguments passed to the If mp_context is None or not given, the default Mp_context can be a multiprocessing context or None. The default chosen will be at most 61, even if more processors are On Windows, max_workers must be less than or equal to 61. If max_workers is less than or equal to 0, then a ValueError Given, it will default to the number of processors on the machine. ProcessPoolExecutor ( max_workers = None, mp_context = None, initializer = None, initargs = () ) ¶Īn Executor subclass that executes calls asynchronously using a pool To a ProcessPoolExecutor will result in deadlock. That ProcessPoolExecutor will not work in the interactive interpreter.Ĭalling Executor or Future methods from a callable submitted The _main_ module must be importable by worker subprocesses. Only picklable objects can be executed and returned. ProcessPoolExecutor uses the multiprocessing module, whichĪllows it to side-step the Global Interpreter Lock but also means that Uses a pool of processes to execute calls asynchronously. The ProcessPoolExecutor class is an Executor subclass that result () except Exception as exc : print ( ' %r generated an exception: %s ' % ( url, exc )) else : print ( ' %r page is %d bytes' % ( url, len ( data ))) ProcessPoolExecutor ¶ as_completed ( future_to_url ): url = future_to_url try : data = future. ThreadPoolExecutor ( max_workers = 5 ) as executor : # Start the load operations and mark each future with its URL future_to_url = for future in concurrent. read () # We can use a with statement to ensure threads are cleaned up promptly with concurrent. urlopen ( url, timeout = timeout ) as conn : return conn. Import concurrent.futures import urllib.request URLS = # Retrieve a single page and report the URL and contents def load_url ( url, timeout ): with urllib. (waiting as if Executor.shutdown() were called with wait set to With statement, which will shutdown the Executor You can avoid having to call this method explicitly if you use the If both cancel_futures and wait are True, all futures that theĮxecutor has started running will be completed prior to this method Any futures thatĪre completed or running won’t be cancelled, regardless of the value If cancel_futures is True, this method will cancel all pendingįutures that the executor has not started running. Value of wait, the entire Python program will not exit until all Return immediately and the resources associated with the executor will beįreed when all pending futures are done executing. Pending futures are done executing and the resources associated with theĮxecutor have been freed. If wait is True then this method will not return until all the Calls toĮxecutor.submit() and Executor.map() made after shutdown will When the currently pending futures are done executing. Signal the executor that it should free any resources that it is using shutdown ( wait = True, *, cancel_futures = False ) ¶ ![]() ThreadPoolExecutor, chunksize has no effect.Ĭhanged in version 3.5: Added the chunksize argument. Performance compared to the default size of 1. ![]() Using a large value for chunksize can significantly improve The (approximate) size of these chunks can be specified by Into a number of chunks which it submits to the pool as separate When using ProcessPoolExecutor, this method chops iterables Raised when its value is retrieved from the iterator. ![]() If a func call raises an exception, then that exception will be None, there is no limit to the wait time. If _next_() is called and the result isn’t availableĪfter timeout seconds from the original call to Executor.map(). The iterables are collected immediately rather than lazily įunc is executed asynchronously and several calls to result ()) map ( func, * iterables, timeout = None, chunksize = 1 ) ¶ submit ( pow, 323, 1235 ) print ( future. With ThreadPoolExecutor ( max_workers = 1 ) as executor : future = executor.
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