wuggy/Dactyloidae
wuggy/Dactyloidae
1
0
Fork 0
mirror of https://repo.dactyloidae.xyz/Dactyloidae/UXP.git synced 2026-09-06 07:48:38 +09:00
Code Issues Projects Releases Packages Wiki Activity

import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

Browse source
This commit is contained in:
Roy Tam 2018-01-19 03:59:58 +08:00
commit dcd9973243
150858 changed files with 23884658 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

347
python/futures/docs/index.rst Normal file
View file

@ -0,0 +1,347 @@
:mod:`concurrent.futures` --- Asynchronous computation
======================================================
.. module:: concurrent.futures
:synopsis: Execute computations asynchronously using threads or processes.
The :mod:`concurrent.futures` module provides a high-level interface for
asynchronously executing callables.
The asynchronous execution can be be performed by threads using
:class:`ThreadPoolExecutor` or seperate processes using
:class:`ProcessPoolExecutor`. Both implement the same interface, which is
defined by the abstract :class:`Executor` class.
Executor Objects
----------------
:class:`Executor` is an abstract class that provides methods to execute calls
asynchronously. It should not be used directly, but through its two
subclasses: :class:`ThreadPoolExecutor` and :class:`ProcessPoolExecutor`.
.. method:: Executor.submit(fn, *args, **kwargs)
Schedules the callable to be executed as *fn*(*\*args*, *\*\*kwargs*) and
returns a :class:`Future` representing the execution of the callable.
::
with ThreadPoolExecutor(max_workers=1) as executor:
future = executor.submit(pow, 323, 1235)
print(future.result())
.. method:: Executor.map(func, *iterables, timeout=None)
Equivalent to map(*func*, *\*iterables*) but func is executed asynchronously
and several calls to *func* may be made concurrently. The returned iterator
raises a :exc:`TimeoutError` if :meth:`__next__()` is called and the result
isn't available after *timeout* seconds from the original call to
:meth:`map()`. *timeout* can be an int or float. If *timeout* is not
specified or ``None`` then there is no limit to the wait time. If a call
raises an exception then that exception will be raised when its value is
retrieved from the iterator.
.. method:: Executor.shutdown(wait=True)
Signal the executor that it should free any resources that it is using when
the currently pending futures are done executing. Calls to
:meth:`Executor.submit` and :meth:`Executor.map` made after shutdown will
raise :exc:`RuntimeError`.
If *wait* is `True` then this method will not return until all the pending
futures are done executing and the resources associated with the executor
have been freed. If *wait* is `False` then this method will return
immediately and the resources associated with the executor will be freed
when all pending futures are done executing. Regardless of the value of
*wait*, the entire Python program will not exit until all pending futures
are done executing.
You can avoid having to call this method explicitly if you use the `with`
statement, which will shutdown the `Executor` (waiting as if
`Executor.shutdown` were called with *wait* set to `True`):
::
import shutil
with ThreadPoolExecutor(max_workers=4) as e:
e.submit(shutil.copy, 'src1.txt', 'dest1.txt')
e.submit(shutil.copy, 'src2.txt', 'dest2.txt')
e.submit(shutil.copy, 'src3.txt', 'dest3.txt')
e.submit(shutil.copy, 'src3.txt', 'dest4.txt')
ThreadPoolExecutor Objects
--------------------------
The :class:`ThreadPoolExecutor` class is an :class:`Executor` subclass that uses
a pool of threads to execute calls asynchronously.
Deadlock can occur when the callable associated with a :class:`Future` waits on
the results of another :class:`Future`. For example:
::
import time
def wait_on_b():
time.sleep(5)
print(b.result()) # b will never complete because it is waiting on a.
return 5
def wait_on_a():
time.sleep(5)
print(a.result()) # a will never complete because it is waiting on b.
return 6
executor = ThreadPoolExecutor(max_workers=2)
a = executor.submit(wait_on_b)
b = executor.submit(wait_on_a)
And:
::
def wait_on_future():
f = executor.submit(pow, 5, 2)
# This will never complete because there is only one worker thread and
# it is executing this function.
print(f.result())
executor = ThreadPoolExecutor(max_workers=1)
executor.submit(wait_on_future)
.. class:: ThreadPoolExecutor(max_workers)
Executes calls asynchronously using at pool of at most *max_workers* threads.
.. _threadpoolexecutor-example:
ThreadPoolExecutor Example
^^^^^^^^^^^^^^^^^^^^^^^^^^
::
from concurrent import futures
import urllib.request
URLS = ['http://www.foxnews.com/',
'http://www.cnn.com/',
'http://europe.wsj.com/',
'http://www.bbc.co.uk/',
'http://some-made-up-domain.com/']
def load_url(url, timeout):
return urllib.request.urlopen(url, timeout=timeout).read()
with futures.ThreadPoolExecutor(max_workers=5) as executor:
future_to_url = dict((executor.submit(load_url, url, 60), url)
for url in URLS)
for future in futures.as_completed(future_to_url):
url = future_to_url[future]
if future.exception() is not None:
print('%r generated an exception: %s' % (url,
future.exception()))
else:
print('%r page is %d bytes' % (url, len(future.result())))
ProcessPoolExecutor Objects
---------------------------
The :class:`ProcessPoolExecutor` class is an :class:`Executor` subclass that
uses a pool of processes to execute calls asynchronously.
:class:`ProcessPoolExecutor` uses the :mod:`multiprocessing` module, which
allows it to side-step the :term:`Global Interpreter Lock` but also means that
only picklable objects can be executed and returned.
Calling :class:`Executor` or :class:`Future` methods from a callable submitted
to a :class:`ProcessPoolExecutor` will result in deadlock.
.. class:: ProcessPoolExecutor(max_workers=None)
Executes calls asynchronously using a pool of at most *max_workers*
processes. If *max_workers* is ``None`` or not given then as many worker
processes will be created as the machine has processors.
.. _processpoolexecutor-example:
ProcessPoolExecutor Example
^^^^^^^^^^^^^^^^^^^^^^^^^^^
::
import math
PRIMES = [
112272535095293,
112582705942171,
112272535095293,
115280095190773,
115797848077099,
1099726899285419]
def is_prime(n):
if n % 2 == 0:
return False
sqrt_n = int(math.floor(math.sqrt(n)))
for i in range(3, sqrt_n + 1, 2):
if n % i == 0:
return False
return True
def main():
with futures.ProcessPoolExecutor() as executor:
for number, prime in zip(PRIMES, executor.map(is_prime, PRIMES)):
print('%d is prime: %s' % (number, prime))
if __name__ == '__main__':
main()
Future Objects
--------------
The :class:`Future` class encapulates the asynchronous execution of a callable.
:class:`Future` instances are created by :meth:`Executor.submit`.
.. method:: Future.cancel()
Attempt to cancel the call. If the call is currently being executed then
it cannot be cancelled and the method will return `False`, otherwise the call
will be cancelled and the method will return `True`.
.. method:: Future.cancelled()
Return `True` if the call was successfully cancelled.
.. method:: Future.running()
Return `True` if the call is currently being executed and cannot be
cancelled.
.. method:: Future.done()
Return `True` if the call was successfully cancelled or finished running.
.. method:: Future.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`` then 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 then this method will raise the same exception.
.. method:: Future.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``
then 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 then ``None`` is returned.
.. method:: Future.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` then it will be logged and ignored. If the
callable raises another :exc:`BaseException` then the behavior is not
defined.
If the future has already completed or been cancelled then *fn* will be
called immediately.
Internal Future Methods
^^^^^^^^^^^^^^^^^^^^^^^
The following :class:`Future` methods are meant for use in unit tests and
:class:`Executor` implementations.
.. method:: Future.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:: Future.set_result(result)
Sets the result of the work associated with the :class:`Future` to *result*.
This method should only be used by Executor implementations and unit tests.
.. method:: Future.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 Executor implementations and unit tests.
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. Returns a named
2-tuple of sets. The first set, named "done", contains the futures that
completed (finished or were cancelled) before the wait completed. The second
set, named "not_done", contains uncompleted 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`` then there is no limit to the wait time.
*return_when* indicates when this function should return. It must be one of
the following constants:
+-----------------------------+----------------------------------------+
| Constant | Description |
+=============================+========================================+
| :const:`FIRST_COMPLETED` | The function will return when any |
| | future finishes or is cancelled. |
+-----------------------------+----------------------------------------+
| :const:`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 |
| | `ALL_COMPLETED`. |
+-----------------------------+----------------------------------------+
| :const:`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 were cancelled). 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.