threading — 线程操作库

用途: 管理多个线程的执行

线程对象

threading_simple.py

import threading


def worker():
    """thread worker function"""
    print('Worker')


threads = []
for i in range(5):
    t = threading.Thread(target=worker)
    threads.append(t)
    t.start()

threading_simpleargs.py

import threading


def worker(num):
    """thread worker function"""
    print('Worker: %s' % num)


threads = []
for i in range(5):
    t = threading.Thread(target=worker, args=(i,))
    threads.append(t)
    t.start()

确定当前线程

import threading
import time


def worker():
    print(threading.current_thread().getName(), 'Starting')
    time.sleep(0.2)
    print(threading.current_thread().getName(), 'Exiting')


def my_service():
    print(threading.current_thread().getName(), 'Starting')
    time.sleep(0.3)
    print(threading.current_thread().getName(), 'Exiting')


t = threading.Thread(name='my_service', target=my_service)
w = threading.Thread(name='worker', target=worker)
w2 = threading.Thread(target=worker)  # use default name

w.start()
w2.start()
t.start()

import logging
import threading
import time


def worker():
    logging.debug('Starting')
    time.sleep(0.2)
    logging.debug('Exiting')


def my_service():
    logging.debug('Starting')
    time.sleep(0.3)
    logging.debug('Exiting')


logging.basicConfig(
    level=logging.DEBUG,
    format='[%(levelname)s] (%(threadName)-10s) %(message)s',
)

t = threading.Thread(name='my_service', target=my_service)
w = threading.Thread(name='worker', target=worker)
w2 = threading.Thread(target=worker)  # use default name

w.start()
w2.start()
t.start()

守护进程与非守护线程

threading_daemon.py

import threading
import time
import logging


def daemon():
    logging.debug('Starting')
    time.sleep(0.2)
    logging.debug('Exiting')


def non_daemon():
    logging.debug('Starting')
    logging.debug('Exiting')


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

d = threading.Thread(name='daemon', target=daemon, daemon=True)

t = threading.Thread(name='non-daemon', target=non_daemon)

d.start()
t.start()

threading_daemon_join.py

import threading
import time
import logging


def daemon():
    logging.debug('Starting')
    time.sleep(0.2)
    logging.debug('Exiting')


def non_daemon():
    logging.debug('Starting')
    logging.debug('Exiting')


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

d = threading.Thread(name='daemon', target=daemon, daemon=True)

t = threading.Thread(name='non-daemon', target=non_daemon)

d.start()
t.start()

d.join()
t.join()

threading_daemon_join_timeout.py

import threading
import time
import logging


def daemon():
    logging.debug('Starting')
    time.sleep(0.2)
    logging.debug('Exiting')


def non_daemon():
    logging.debug('Starting')
    logging.debug('Exiting')


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

d = threading.Thread(name='daemon', target=daemon, daemon=True)

t = threading.Thread(name='non-daemon', target=non_daemon)

d.start()
t.start()

d.join(0.1)
print('d.isAlive()', d.isAlive())
t.join()

列举所有线程

threading_enumerate.py

# threading_enumerate.py

import random
import threading
import time
import logging


def worker():
    """thread worker function"""
    pause = random.randint(1, 5) / 10
    logging.debug('sleeping %0.2f', pause)
    time.sleep(pause)
    logging.debug('ending')


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

for i in range(3):
    t = threading.Thread(target=worker, daemon=True)
    t.start()

main_thread = threading.main_thread()
for t in threading.enumerate():
    if t is main_thread:
        continue
    logging.debug('joining %s', t.getName())
    t.join()

子类化线程

# threading_subclass.py
import threading
import logging


class MyThread(threading.Thread):

    def run(self):
        logging.debug('running')


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

for i in range(5):
    t = MyThread()
    t.start()

# threading_subclass_args.py
import threading
import logging


class MyThreadWithArgs(threading.Thread):

    def __init__(self, group=None, target=None, name=None,
                 args=(), kwargs=None, *, daemon=None):
        super().__init__(group=group, target=target, name=name,
                         daemon=daemon)
        self.args = args
        self.kwargs = kwargs

    def run(self):
        logging.debug('running with %s and %s',
                      self.args, self.kwargs)


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

for i in range(5):
    t = MyThreadWithArgs(args=(i,), kwargs={'a': 'A', 'b': 'B'})
    t.start()

定时器线程

# threading_timer.py

import threading
import time
import logging


def delayed():
    logging.debug('worker running')


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

t1 = threading.Timer(0.3, delayed)
t1.setName('t1')
t2 = threading.Timer(0.3, delayed)
t2.setName('t2')

logging.debug('starting timers')
t1.start()
t2.start()

logging.debug('waiting before canceling %s', t2.getName())
time.sleep(0.2)
logging.debug('canceling %s', t2.getName())
t2.cancel()
logging.debug('done')

线程之间发信号

# threading_event.py
import logging
import threading
import time


def wait_for_event(e):
    """Wait for the event to be set before doing anything"""
    logging.debug('wait_for_event starting')
    event_is_set = e.wait()
    logging.debug('event set: %s', event_is_set)


def wait_for_event_timeout(e, t):
    """Wait t seconds and then timeout"""
    while not e.is_set():
        logging.debug('wait_for_event_timeout starting')
        event_is_set = e.wait(t)
        logging.debug('event set: %s', event_is_set)
        if event_is_set:
            logging.debug('processing event')
        else:
            logging.debug('doing other work')


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

e = threading.Event()
t1 = threading.Thread(
    name='block',
    target=wait_for_event,
    args=(e,),
)
t1.start()

t2 = threading.Thread(
    name='nonblock',
    target=wait_for_event_timeout,
    args=(e, 2),
)
t2.start()

logging.debug('Waiting before calling Event.set()')
time.sleep(0.3)
e.set()
logging.debug('Event is set')

控制资源访问

# threading_lock.py
import logging
import random
import threading
import time


class Counter:

    def __init__(self, start=0):
        self.lock = threading.Lock()
        self.value = start

    def increment(self):
        logging.debug('Waiting for lock')
        self.lock.acquire()
        try:
            logging.debug('Acquired lock')
            self.value = self.value + 1
        finally:
            self.lock.release()


def worker(c):
    for i in range(2):
        pause = random.random()
        logging.debug('Sleeping %0.02f', pause)
        time.sleep(pause)
        c.increment()
    logging.debug('Done')


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

counter = Counter()
for i in range(2):
    t = threading.Thread(target=worker, args=(counter,))
    t.start()

logging.debug('Waiting for worker threads')
main_thread = threading.main_thread()
for t in threading.enumerate():
    if t is not main_thread:
        t.join()
logging.debug('Counter: %d', counter.value)

# threading_lock_noblock.py
import logging
import threading
import time


def lock_holder(lock):
    logging.debug('Starting')
    while True:
        lock.acquire()
        try:
            logging.debug('Holding')
            time.sleep(0.5)
        finally:
            logging.debug('Not holding')
            lock.release()
        time.sleep(0.5)


def worker(lock):
    logging.debug('Starting')
    num_tries = 0
    num_acquires = 0
    while num_acquires < 3:
        time.sleep(0.5)
        logging.debug('Trying to acquire')
        have_it = lock.acquire(0)
        try:
            num_tries += 1
            if have_it:
                logging.debug('Iteration %d: Acquired',
                              num_tries)
                num_acquires += 1
            else:
                logging.debug('Iteration %d: Not acquired',
                              num_tries)
        finally:
            if have_it:
                lock.release()
    logging.debug('Done after %d iterations', num_tries)


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

lock = threading.Lock()

holder = threading.Thread(
    target=lock_holder,
    args=(lock,),
    name='LockHolder',
    daemon=True,
)
holder.start()

worker = threading.Thread(
    target=worker,
    args=(lock,),
    name='Worker',
)
worker.start()

重入锁

# threading_lock_reacquire.py
import threading

lock = threading.Lock()

print('First try :', lock.acquire())
print('Second try:', lock.acquire(0))

# threading_rlock.py
import threading

lock = threading.RLock()

print('First try :', lock.acquire())
print('Second try:', lock.acquire(0))

锁作为上下文管理器

# threading_lock_with.py
import threading
import logging


def worker_with(lock):
    with lock:
        logging.debug('Lock acquired via with')


def worker_no_with(lock):
    lock.acquire()
    try:
        logging.debug('Lock acquired directly')
    finally:
        lock.release()


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

lock = threading.Lock()
w = threading.Thread(target=worker_with, args=(lock,))
nw = threading.Thread(target=worker_no_with, args=(lock,))

w.start()
nw.start()

线程同步

# threading_condition.py
import logging
import threading
import time


def consumer(cond):
    """wait for the condition and use the resource"""
    logging.debug('Starting consumer thread')
    with cond:
        cond.wait()
        logging.debug('Resource is available to consumer')


def producer(cond):
    """set up the resource to be used by the consumer"""
    logging.debug('Starting producer thread')
    with cond:
        logging.debug('Making resource available')
        cond.notifyAll()


logging.basicConfig(
    level=logging.DEBUG,
    format='%(asctime)s (%(threadName)-2s) %(message)s',
)

condition = threading.Condition()
c1 = threading.Thread(name='c1', target=consumer,
                      args=(condition,))
c2 = threading.Thread(name='c2', target=consumer,
                      args=(condition,))
p = threading.Thread(name='p', target=producer,
                     args=(condition,))

c1.start()
time.sleep(0.2)
c2.start()
time.sleep(0.2)
p.start()

# threading_barrier.py
import threading
import time


def worker(barrier):
    print(threading.current_thread().name,
          'waiting for barrier with {} others'.format(
              barrier.n_waiting))
    worker_id = barrier.wait()
    print(threading.current_thread().name, 'after barrier',
          worker_id)


NUM_THREADS = 3

barrier = threading.Barrier(NUM_THREADS)

threads = [
    threading.Thread(
        name='worker-%s' % i,
        target=worker,
        args=(barrier,),
    )
    for i in range(NUM_THREADS)
]

for t in threads:
    print(t.name, 'starting')
    t.start()
    time.sleep(0.1)

for t in threads:
    t.join()

# threading_barrier_abort.py
import threading
import time


def worker(barrier):
    print(threading.current_thread().name,
          'waiting for barrier with {} others'.format(
              barrier.n_waiting))
    try:
        worker_id = barrier.wait()
    except threading.BrokenBarrierError:
        print(threading.current_thread().name, 'aborting')
    else:
        print(threading.current_thread().name, 'after barrier',
              worker_id)


NUM_THREADS = 3

barrier = threading.Barrier(NUM_THREADS + 1)

threads = [
    threading.Thread(
        name='worker-%s' % i,
        target=worker,
        args=(barrier,),
    )
    for i in range(NUM_THREADS)
]

for t in threads:
    print(t.name, 'starting')
    t.start()
    time.sleep(0.1)

barrier.abort()

for t in threads:
    t.join()

限制并发资源访问

# threading_semaphore.py
import logging
import random
import threading
import time


class ActivePool:

    def __init__(self):
        super(ActivePool, self).__init__()
        self.active = []
        self.lock = threading.Lock()

    def makeActive(self, name):
        with self.lock:
            self.active.append(name)
            logging.debug('Running: %s', self.active)

    def makeInactive(self, name):
        with self.lock:
            self.active.remove(name)
            logging.debug('Running: %s', self.active)


def worker(s, pool):
    logging.debug('Waiting to join the pool')
    with s:
        name = threading.current_thread().getName()
        pool.makeActive(name)
        time.sleep(0.1)
        pool.makeInactive(name)


logging.basicConfig(
    level=logging.DEBUG,
    format='%(asctime)s (%(threadName)-2s) %(message)s',
)

pool = ActivePool()
s = threading.Semaphore(2)
for i in range(4):
    t = threading.Thread(
        target=worker,
        name=str(i),
        args=(s, pool),
    )
    t.start()

线程私有的数据

# threading_local.py

import random
import threading
import logging


def show_value(data):
    try:
        val = data.value
    except AttributeError:
        logging.debug('No value yet')
    else:
        logging.debug('value=%s', val)


def worker(data):
    show_value(data)
    data.value = random.randint(1, 100)
    show_value(data)


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

local_data = threading.local()
show_value(local_data)
local_data.value = 1000
show_value(local_data)

for i in range(2):
    t = threading.Thread(target=worker, args=(local_data,))
    t.start()

# threading_local_defaults.py
import random
import threading
import logging


def show_value(data):
    try:
        val = data.value
    except AttributeError:
        logging.debug('No value yet')
    else:
        logging.debug('value=%s', val)


def worker(data):
    show_value(data)
    data.value = random.randint(1, 100)
    show_value(data)


class MyLocal(threading.local):

    def __init__(self, value):
        super().__init__()
        logging.debug('Initializing %r', self)
        self.value = value


logging.basicConfig(
    level=logging.DEBUG,
    format='(%(threadName)-10s) %(message)s',
)

local_data = MyLocal(1000)
show_value(local_data)

for i in range(2):
    t = threading.Thread(target=worker, args=(local_data,))
    t.start()