Python3 ThreadPoolExecutor--线程池
1、线程池创建
def __init__(self,
max_workers=None,
thread_name_prefix='',
initializer=None,
initargs=())max_workers: 设置线程池中最多能同时运行的线程数目
thread_name_prefix：一个可选的名称前缀，用于给线程命名
initializer : 线程可回调的函数
initargs: initializer 的参数
2、submit
提交线程需要执行的任务（函数名和参数）到线程池中，并返回该任务的句柄
def submit(self, fn, /, *args, **kwargs):即将fn函数提交给线程池，*args代表传给fn函数的参数，**kwargs代表以关键字参数的形式为fn函数传入参数。
def submit(self, fn, /, *args, **kwargs):
with self._shutdown_lock, _global_shutdown_lock:
if self._broken:
raise BrokenThreadPool(self._broken)
if self._shutdown:
raise RuntimeError('cannot schedule new futures after shutdown')
if _shutdown:
raise RuntimeError('cannot schedule new futures after '
'interpreter shutdown')
f = _base.Future()
w = _WorkItem(f, fn, args, kwargs)
self._work_queue.put(w)
self._adjust_thread_count()
return fsubmit 函数返回的为 future 对象 ，future 各个方法如下：
class Future(Generic[_T]):
# 初始化
def __init__(self) -> None: ...
# Returns True if the future was cancelled, False otherwise. A future
cannot be cancelled if it is running or has already completed.
def cancel(self) -> bool: ...
# Return True if the future was cancelled.
def cancelled(self) -> bool: ...
# Return True if the future is currently executing
def running(self) -> bool: ...
# Return True of the future was cancelled or finished executing
def done(self) -> bool: ...
#"""Attaches a callable that will be called when the future finishes.
Args:
fn: A callable that will be called with this future as its only
argument when the future completes or is cancelled. The callable
will always be called by a thread in the same process in which
it was added. If the future has already completed or been
cancelled then the callable will be called immediately. These
callables are called in the order that they were added.
"""
def add_done_callback(self, fn: Callable[[Future[_T]], Any]) -> None: ...
#"""Return the result of the call that the future represents.
Args:
timeout: The number of seconds to wait for the result if the future
isn't done. If None, then there is no limit on the wait time.
Returns:
The result of the call that the future represents.
Raises:
CancelledError: If the future was cancelled.
TimeoutError: If the future didn't finish executing before the given
timeout.
Exception: If the call raised then that exception will be raised.
阻塞式的获取任务的返回值
"""
def result(self, timeout: float | None = ...) -> _T: ...
#"""Mark the future as running or process any cancel notifications.
Should only be used by Executor implementations and unit tests.
If the future has been cancelled (cancel() was called and returned
True) then any threads waiting on the future completing (though calls
to as_completed() or wait()) are notified and False is returned.
If the future was not cancelled then it is put in the running state
(future calls to running() will return True) and True is returned.
This method should be called by Executor implementations before
executing the work associated with this future. If this method returns
False then the work should not be executed.
Returns:
False if the Future was cancelled, True otherwise.
Raises:
RuntimeError: if this method was already called or if set_result()
or set_exception() was called.
"""
def set_running_or_notify_cancel(self) -> bool: ...
#"""Sets the return value of work associated with the future.
Should only be used by Executor implementations and unit tests.
"""
def set_result(self, result: _T) -> None: ...
#"""Return the exception raised by the call that the future represents.
Args:
timeout: The number of seconds to wait for the exception if the
future isn't done. If None, then there is no limit on the wait
time.
Returns:
The exception raised by the call that the future represents or None
if the call completed without raising.
Raises:
CancelledError: If the future was cancelled.
TimeoutError: If the future didn't finish executing before the given
timeout.
"""
def exception(self, timeout: float | None = ...) -> BaseException | None: ...
#"""Return the exception raised by the call that the future represents.
Args:
timeout: The number of seconds to wait for the exception if the
future isn't done. If None, then there is no limit on the wait
time.
Returns:
The exception raised by the call that the future represents or None
if the call completed without raising.
Raises:
CancelledError: If the future was cancelled.
TimeoutError: If the future didn't finish executing before the given
timeout.
"""
def set_exception(self, exception: BaseException | None) -> None: ...
3、as_completed
一次取出所有任务的结果,详情请看 as_completed 源码,tasks 为 submit 返回的 future 列表
from concurrent.futures import ThreadPoolExecutor, as_completed
for future in as_completed(tasks):
data = future.result()
4、map
另一种获取线程池返回结果的方法
def map(self, fn, *iterables, timeout=None, chunksize=1):
"""Returns an iterator equivalent to map(fn, iter).
Args:
fn: A callable that will take as many arguments as there are
passed iterables.
timeout: The maximum number of seconds to wait. If None, then there
is no limit on the wait time.
chunksize: The size of the chunks the iterable will be broken into
before being passed to a child process. This argument is only
used by ProcessPoolExecutor; it is ignored by
ThreadPoolExecutor.
Returns:
An iterator equivalent to: map(func, *iterables) but the calls may
be evaluated out-of-order.
Raises:
TimeoutError: If the entire result iterator could not be generated
before the given timeout.
Exception: If fn(*args) raises for any values.
"""5、wait
方法可以让主线程阻塞，直到满足设定的要求。tasks 为 submit 返回的 future 列表
from concurrent.futures import ThreadPoolExecutor, wait, ALL_COMPLETED, FIRST_COMPLETED
wait(tasks, return_when=ALL_COMPLETED)
def wait(fs, timeout=None, return_when=ALL_COMPLETED):
"""Wait for the futures in the given sequence to complete.
Args:
fs: The sequence of Futures (possibly created by different Executors) to
wait upon.
timeout: The maximum number of seconds to wait. If None, then there
is no limit on the wait time.
return_when: Indicates when this function should return. The options
are:
FIRST_COMPLETED - Return when any future finishes or is
cancelled.
FIRST_EXCEPTION - Return when any future finishes by raising an
exception. If no future raises an exception
then it is equivalent to ALL_COMPLETED.
ALL_COMPLETED - Return when all futures finish or are cancelled.
Returns:
A named 2-tuple of sets. The first set, named 'done', contains the
futures that completed (is finished or cancelled) before the wait
completed. The second set, named 'not_done', contains uncompleted
futures. Duplicate futures given to *fs* are removed and will be
returned only once.
"""