Pool
- Pool([processes[, initializer[, initargs[, maxtasksperchild[, context]]]]])
Class which supports an async version of applying functions to arguments.
© Python Software Foundation. PSF License Version 2 · Official docs ↗
Changed in 3.2, 3.3, 3.4, 3.13
- 3.2: Added the maxtasksperchild parameter.
- 3.3: Pool objects now support the context management protocol – see Context Manager Types. __enter__() returns the pool object, and __exit__() calls terminate().
- 3.4: Added the context parameter.
- 3.13: processes uses os.process_cpu_count() by default, instead of os.cpu_count().
Members of Pool
a
- apply
- Equivalent of `func(*args, **kwds)`.
- apply_async
- Asynchronous version of `apply()` method.
c
- close
- Prevents any more tasks from being submitted to the pool.
i
- imap
- Equivalent of `map()` -- can be MUCH slower than `Pool.map()`.
- imap_unordered
- Like `imap()` method but ordering of results is arbitrary.
j
- join
- Wait for the worker processes to exit.
m
s
- starmap
- Like `map()` method but the elements of the `iterable` are expected to be iterables as well and will be unpacked as arguments.
- starmap_async
- Asynchronous version of `starmap()` method.
t
- terminate
- Stops the worker processes immediately without completing outstanding work.
1 Example
>>> from multiprocessing import Pool >>> p = Pool(5) >>> def f(x): ... return x*x ... >>> with p: ... p.map(f, [1,2,3]) Process PoolWorker-1: Process PoolWorker-2: Process PoolWorker-3: Traceback (most recent call last): Traceback (most recent call last): Traceback (most recent call last): AttributeError: Can't get attribute 'f' on <module '__main__' (<class '_frozen_importlib.BuiltinImporter'>)> AttributeError: Can't get attribute 'f' on <module '__main__' (<class '_frozen_importlib.BuiltinImporter'>)> AttributeError: Can't get attribute 'f' on <module '__main__' (<class '_frozen_importlib.BuiltinImporter'>)>
from the Python docs