📅  最后修改于: 2023-12-03 15:19:31.712000             🧑  作者: Mango
Python是一种支持多线程编程的编程语言。在Python中,使用threading
模块可以轻松地创建线程,实现多任务并行处理。
线程是操作系统能够进行运算调度的最小单位,它被包含在进程中,是进程中的实际运作单位。线程是轻量级的进程,它可以与其他线程共享内存,这使得进程产生了轻量级的特性。
在Python中,可以通过threading.Thread()
函数创建线程。例:
import threading
class myThread(threading.Thread):
def __init__(self, threadID, name, counter):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.counter = counter
def run(self):
print("开始线程:" + self.name)
print_time(self.name, self.counter, 5)
print("退出线程:" + self.name)
def print_time(threadName, delay, counter):
while counter:
time.sleep(delay)
print("%s: %s" % (threadName, time.ctime(time.time())))
counter -= 1
if __name__ == '__main__':
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)
thread1.start()
thread2.start()
thread1.join()
thread2.join()
print("退出主线程")
在上述例子中,我们定义了一个类myThread
继承了threading.Thread
类,并实现了run()
方法。通过实例化myThread
类,我们创建了两个线程:thread1
和thread2
。通过start()
方法启动线程,通过join()
方法等待线程结束。
在并发编程中,线程同步是非常重要的。Python中可以通过threading.Lock()
函数实现资源访问的同步。例:
import threading
class myThread(threading.Thread):
def __init__(self, threadID, name, counter):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.counter = counter
def run(self):
print("开始线程:" + self.name)
threadLock.acquire()
print_time(self.name, self.counter, 5)
threadLock.release()
print("退出线程:" + self.name)
def print_time(threadName, delay, counter):
while counter:
time.sleep(delay)
print("%s: %s" % (threadName, time.ctime(time.time())))
counter -= 1
threadLock = threading.Lock()
if __name__ == '__main__':
threads = []
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)
thread1.start()
thread2.start()
threads.append(thread1)
threads.append(thread2)
for t in threads:
t.join()
print("退出主线程")
在上述例子中,我们使用了threading.Lock()
函数创建了一个线程锁threadLock
。在myThread
中,我们通过acquire()
方法获取锁,通过release()
方法释放锁,以实现资源访问的同步。
在并发编程中,线程优先级队列用于确保高优先级的线程先被调度执行。Python中可以通过Queue.PriorityQueue()
函数实现线程优先级队列。例:
import queue
import threading
class myThread(threading.Thread):
def __init__(self, threadID, name, q):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.q = q
def run(self):
print("开始线程:" + self.name)
process_data(self.name, self.q)
print("退出线程:" + self.name)
def process_data(threadName, q):
while not exitFlag:
queueLock.acquire()
if not workQueue.empty():
data = q.get()
queueLock.release()
print("%s processing %s" % (threadName, data))
else:
queueLock.release()
time.sleep(1)
threadList = ["Thread-1", "Thread-2", "Thread-3"]
nameList = ["One", "Two", "Three", "Four", "Five"]
queueLock = threading.Lock()
workQueue = queue.PriorityQueue(10)
threads = []
threadID = 1
exitFlag = 0
if __name__ == '__main__':
# 创建新线程
for tName in threadList:
thread = myThread(threadID, tName, workQueue)
thread.start()
threads.append(thread)
threadID += 1
# 填充队列
queueLock.acquire()
for word in nameList:
workQueue.put(word)
queueLock.release()
# 等待队列清空
while not workQueue.empty():
pass
# 通知线程退出
exitFlag = 1
# 等待所有线程完成
for t in threads:
t.join()
print("退出主线程")
在上述例子中,我们使用了queue.PriorityQueue()
函数创建了一个线程优先级队列workQueue
。在myThread
中,我们通过get()
和put()
方法从队列中获取和插入数据,以实现线程优先级调度。
Python中多线程的创建和使用非常方便,可以充分发挥多核CPU的性能,提高程序的效率。在编写多线程代码时,需要注意线程同步和线程优先级队列的处理,以保证程序的正确性和性能。