多线程

全局解释器(GIL)

• Python 代码的执行由Python虚拟机进行控制
• 在主循环中只能有一个控制线程在执行

Python包

• thread包存在问题,在python3中改成了_thread
• threading:通行的包
  • threading的使用
    • 直接使用threading.Thread生成Thread
    1. t = threading.Thread(target=xxx, args=(xxx,))
    2. t.start();启动线程
    3. t.join();等待线程完成
• 守护线程 daemon
  • 如果在程序子线程设置成守护线程,则子线程会在主线程结束的时候自动结束
  • 一般认为,守护线程不重要或者不允许离开主线程独立运行
  • 守护线程案例能否有效果跟环境有关

# 多线程 案例1
import time
import _thread as thread

def loop1():
    # ctime 获取当前时间
    print("start loop 1 at :",time.ctime())
    
    #休眠4秒
    time.sleep(4)
    print("end loop 1 at :",time.ctime())
    
def loop2():
    # ctime 获取当前时间
    print("start loop 2 at :",time.ctime())
    
    #休眠4秒
    time.sleep(2)
    print("end loop 2 at :",time.ctime())
    
def main():
    print("start at :",time.ctime())
    thread.start_new_thread(loop1,())
    thread.start_new_thread(loop2,())
    print("all done at :",time.ctime())
    
if __name__ == '__main__':
    main()

start at : Sun Mar  3 22:41:12 2019
all done at : Sun Mar  3 22:41:12 2019
start loop 2 at : Sun Mar  3 22:41:12 2019
start loop 1 at : Sun Mar  3 22:41:12 2019
end loop 2 at : Sun Mar  3 22:41:14 2019
end loop 1 at : Sun Mar  3 22:41:16 2019

# 多线程 案例2
import time
import _thread as thread

def loop1(int1):
    # ctime 获取当前时间
    print("start loop 1 at :",time.ctime())
    print("我是参数:",int1)
    #休眠4秒
    time.sleep(4)
    print("end loop 1 at :",time.ctime())
    
def loop2(int1, int2):
    # ctime 获取当前时间
    print("start loop 2 at :",time.ctime())
    print("我是参数1:{0},我是参数2:{1}".format(int1,int2))
    #休眠4秒
    time.sleep(2)
    print("end loop 2 at :",time.ctime())
    
def main():
    print("start at :",time.ctime())
    thread.start_new_thread(loop1,("王老大",))
    thread.start_new_thread(loop2,("张三","李四"))
    print("all done at :",time.ctime())
    
if __name__ == '__main__':
    main()

start at : Sun Mar  3 22:43:48 2019
all done at : Sun Mar  3 22:43:48 2019
start loop 2 at : Sun Mar  3 22:43:48 2019
我是参数1:张三,我是参数2:李四
start loop 1 at : Sun Mar  3 22:43:48 2019
我是参数: 王老大
end loop 2 at : Sun Mar  3 22:43:50 2019
end loop 1 at : Sun Mar  3 22:43:52 2019

# 多线程 案例3
import time
import threading

def loop1(int1):
    # ctime 获取当前时间
    print("start loop 1 at :",time.ctime())
    print("我是参数:",int1)
    #休眠4秒
    time.sleep(4)
    print("end loop 1 at :",time.ctime())
    
def loop2(int1, int2):
    # ctime 获取当前时间
    print("start loop 2 at :",time.ctime())
    print("我是参数1:{0},我是参数2:{1}".format(int1,int2))
    #休眠4秒
    time.sleep(2)
    print("end loop 2 at :",time.ctime())
    
def main():
    print("start at :",time.ctime())
    t1 = threading.Thread(target=loop1, args=("王小虎",))
    t2 = threading.Thread(target=loop2, args=("熊大","熊二"))
    t1.start()
    t2.start()
    
    t1.join()
    t2.join()
    print("all done at :",time.ctime())
    
if __name__ == '__main__':
    main()

start at : Sun Mar  3 22:53:12 2019
start loop 1 at : Sun Mar  3 22:53:12 2019
我是参数: 王小虎
start loop 2 at : Sun Mar  3 22:53:12 2019
我是参数1:熊大,我是参数2:熊二
end loop 2 at : Sun Mar  3 22:53:14 2019
end loop 1 at : Sun Mar  3 22:53:16 2019
all done at : Sun Mar  3 22:53:16 2019

# 守护线程 案例1
import time
import threading

def fun():
    print("start fun")
    time.sleep(2)
    print("end fun")
    
print("Main start")
t = threading.Thread(target= fun, args=())
t.setDaemon(True)
t.start()
time.sleep(1)
print("Main end")

Main start
start fun
Main end
end fun

线程的当用属性

• threading.currentThread: 返回当前线程变量
• threading.activeCount: 返回正在运行的线程数量
• threading.enumerate: 返回一个包含正在运行的线程的list
• threading.setName:给线程设置名字
• threading.getName:返回线程的名字

直接继承自threading.Thread

• 直接继承Thread
• 重写run方法
• 类实例可以直接运行