Python高级：多线程（MultiThread）

最近在用python的多线程处理一些数据。

示例一

import threading
import time

def thread_job():   #该任务比较消耗时间
    print("T1 start\n")
    for i in range(10):
        time.sleep(0.1)
    print("T1 finish\n")

def T2_job():
    print("T2 start\n")
    print("T2 finish\n")

def main():
    added_thread=threading.Thread(target=thread_job,name="T1")
    thread2=threading.Thread(target=T2_job,name="T2")
    added_thread.start()
    thread2.start()
    thread2.join()    #join的作用是不让主线程比某个thread先结束
    print("all done\n")

if __name__ == '__main__':
    main()

输出为：

示例二

import threading
import time

li = [0 for i in range(12)]

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("开启线程" + self.name)
        #threadLock.acquire()
        print_time(self.name,self.counter,len(li))
        #threadLock.release()

    def __del__(self):
        print(self.name+"线程结束！")


def print_time(threadName, delay, counter):
    while counter:
        time.sleep(delay)
        li[counter - 1] += 1
        print("[%s] %s修改%d个值，修改后为：%d" % (time.ctime(time.time()), threadName, counter, li[counter - 1]))
        counter -= 1


threadLock = threading.Lock()
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("主进程结束")

输出：

示例三

import threading
from queue import Queue

def job(li,q):
    for i in range(len(li)):
        li[i]=li[i]**2
    q.put(li)

def multithreading():
    q=Queue()
    threads=[]
    data=[[1,2,3],[3,4,5],[5,6,7],[7,8,9]]
    for i in range(4):
        t=threading.Thread(target=job,args=(data[i],q))
        t.start()
        threads.append(t)
    for thread in threads:
        thread.join()
    results=[]
    for _ in range(4):
        results.append(q.get())
    print(results)
if __name__ == '__main__':
    multithreading()

输出如下：

示例四

import threading
from queue import Queue
import copy
import time

def job(li,q):
    res=sum(li)
    q.put(res)

def multithreading(l):
    q=Queue()
    threads=[]
    for i in range(4):
        t=threading.Thread(target=job,args=(copy.copy(l),q))
        t.start()
        threads.append(t)
    [t.join() for t in threads]
    total=0
    for _ in range(4):
        total+=q.get()
    print(total)

def normal(l):
    total=sum(l)
    print(total)


if __name__=="__main__":
    l=list(range(1000000))
    s_time=time.time()
    normal(l*4)
    print("normal "+str(time.time()-s_time))
    s_time=time.time()
    multithreading(l)
    print("multithreading: "+str(time.time()-s_time))

输出如下：多线程的速度确实比普通的快一些，我在IDE里运行的差距不明显

示例五

import threading

def job1():
    global A,lock
    lock.acquire()
    for i in range(10):
        A+=1
        print("job1",A)
    lock.release()

def job2():
    global A,lock
    lock.acquire()
    for i in range(10):
        A+=10
        print("job2",A)
    lock.release()

if __name__=='__main__':
    lock=threading.Lock()
    A=0
    t1=threading.Thread(target=job1)
    t2=threading.Thread(target=job2)
    t1.start()
    t2.start()

这里加了锁之后的执行跟顺序执行一致

示例六

import threading

def job1():
    global A
    for i in range(10):
        A+=1
        print("job1",A)

def job2():
    global A
    for i in range(10):
        A+=10
        print("job2",A)

if __name__=='__main__':
    A=0
    t1=threading.Thread(target=job1)
    t2=threading.Thread(target=job2)
    t1.start()
    t2.start()
    t2.join()
    t3=threading.Thread(target=job1)
    t3.start()

这是一个多线程修改全局变量的例子（共享数据）
运行结果如下