Python3 多任务之---线程

多线程 threading 模块

• 方式一

import threading    #或from threading import Thread
import time

def test():
    print('线程输出……')
    time.sleep(1)

if __name__ == '__main__':
    for i in range(5):
        t = threading.Thread(target=test)
        t.start()

• 方式二：继承类的方法

import threading
import time

class MyThread(threading.Thread):
    def run(self):
        for i in range(3):
            time.sleep(1)
            msg = "I'm"+self.name+' @ '+str(i)    #name 中保存的是当前线程名字
            print(msg)

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

if __name__ == '__main__':
    test()

• 线程共享全局变量：global

互斥锁

• 创建锁（默认不上锁）
  
  mutex = threading.Lock()
• 锁定
  
  mutex.acquire([blocking])
• 释放
  
  mutex.release()
• 上锁代码，越少越好

避免死锁

• 程序设计时要尽量避免（银行家算法）
• 添加超时时间等（mutex.acquire(timeout=2)）

生产者与消费者模式

• 进程间使用队列

from queue import Queue
queue = Queue()
queue.put('添加')
queue.get()    #获取队列数据
queue.qsize()  #队列大小

import threading
from queue import Queue
import time

class A(threading.Thread):
    def run(self):
        global queue
        while True:
            if queue.qsize()<=50:
                for i in range(100):
                    queue.put('产品'+str(i))
                    print(self.name+'生产产品'+str(i))
                    time.sleep(0.2)

class B(threading.Thread):
    def run(self):
        global queue
        while True:
            if queue.qsize() >= 50:
                for i in range(10):
                    q = queue.get()
                    print(self.name+'消费'+q)
                    time.sleep(0.5)
                
queue = Queue()
for i in range(10):
    queue.put('初始产品'+str(i))

for i in range(2):
    a = A()
    a.start()

for i in range(5):
    b = B()
    b.start()

全局字典

global_dict = {}

def std_thread(name):
    std = Student(name)
    global_dict[threading.current_thread()] = std
    do_task_1()
    do_task_2()

def do_task_1():
    std = global_dict[threading.current_thread()]
    ……

def do_task_2():
    std = global_dict[threading.current_thread()]
    ……

ThreadLocal 方式

import threading

local_school = threading.local()

def process_student():
    std = local_school.student
    print('hello,%s(in %s)'%(std,threading.current_thread().name))

def process_thread(name):
    local_school.student = name
    process_student()

t1 = threading.Thread(target=process_thread,args=('dongGe',),name='Thread-A')
t1 = threading.Thread(target=process_thread,args=('老王',),name='Thread-B')
t1.start()
t2.start()
t1.join()
t2.join()