Python-多线程
进程-进程有自己的完全独立的运行环境，多进程共享数据是个问题
线程-一个进程独立运行的片段，一个进程可以有多个线程
全局解释器（GTL）
-python代码的执行是由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：之前应用的版本，python3改成了_thread
-threading：先行通行的包
1. * 1. 学习python加python编程语言学习 QQ群515267276
案例
'''
利用time函数生成两个函数，顺序调用，计算总的计算时间
'''
import time
def loop1():
#ctime得到当前时间
print("start loop1 at ",time.ctime())
#sleep
time.sleep(4)
print("end loop1 at",time.ctime())
def loop2():
print("start loop2 at ", time.ctime())
# sleep
time.sleep(2)
print("end loop2 at", time.ctime())
def main():
print("start at",time.ctime())
loop1()
loop2()
print("all done at ",time.ctime())
if name=="main":
main()
运行结果如下：
start at Mon Jan 7 09:18:44 2019
start loop1 at Mon Jan 7 09:18:44 2019
end loop1 at Mon Jan 7 09:18:48 2019
start loop2 at Mon Jan 7 09:18:48 2019
end loop2 at Mon Jan 7 09:18:50 2019
all done at Mon Jan 7 09:18:50 2019
案例2（案例1使用多线程）
def loop1():
#ctime得到当前时间
print("start loop1 at ",time.ctime())
#sleep
time.sleep(4)
print("end loop1 at",time.ctime())
def loop2():
print("start loop2 at ", time.ctime())
# sleep
time.sleep(2)
print("end loop2 at", time.ctime())
def main():
print("start at",time.ctime())
#启动多线程的意思使用多线程去执行某个函数
threading.Thread(target=loop1).start()
threading.Thread(target=loop2).start()
print("all done at ",time.ctime())
if name=="main":
main()
20
运行结果如下：
start at Mon Jan 7 09:31:46 2019
start loop1 at Mon Jan 7 09:31:46 2019
start loop2 at Mon Jan 7 09:31:46 2019
all done at Mon Jan 7 09:31:46 2019
end loop2 at Mon Jan 7 09:31:48 2019
end loop1 at Mon Jan 7 09:31:50 2019
案例3（多线程+参数）
import time
import threading
import _thread as thread
def loop1(in1):
#ctime得到当前时间
print("start loop1 at ",time.ctime())
print("gram1",in1)
#sleep
time.sleep(4)
print("end loop1 at",time.ctime())
def loop2(in1,in2):
print("start loop2 at ", time.ctime())
# sleep
print("gram1",in1,"gram2",in2)
time.sleep(2)
print("end loop2 at", time.ctime())
def main():
print("start at",time.ctime())
#启动多线程的意思使用多线程去执行某个函数
#启动多线程的函数为start_new_thread
#参数有两个一个是需要运行的函数，另一个参数作为元祖使用
#如果有一个参数时一定要价格逗号
thread.start_new_thread(loop1,("beijing",))
thread.start_new_thread(loop2,("tianjin","hangzhou"))
print("all done at ",time.ctime())
if name=="main":
main()
while True:
time.sleep(8)
运行结果如下：
start at Mon Jan 7 09:50:48 2019
all done at Mon Jan 7 09:50:48 2019
start loop1 at Mon Jan 7 09:50:48 2019
gram1 beijing
start loop2 at Mon Jan 7 09:50:48 2019
gram1 tianjin gram2 hangzhou
end loop2 at Mon Jan 7 09:50:50 2019
end loop1 at Mon Jan 7 09:50:52 2019
threading的使用
-t=threading.Thread(target=XXX,args=(xxx,))
-t.start():启动多线程
-t.join():等待多线程执行完成
案例04
import time
import threading
import _thread as thread
def loop1(in1):
#ctime得到当前时间
print("start loop1 at ",time.ctime())
print("gram1",in1)
#sleep
time.sleep(4)
print("end loop1 at",time.ctime())
def loop2(in1,in2):
print("start loop2 at ", time.ctime())
# sleep
print("gram1",in1,"gram2",in2)
time.sleep(2)
print("end loop2 at", time.ctime())
def main():
print("start at",time.ctime())
#启动多线程的意思使用多线程去执行某个函数
t1=threading.Thread(target=loop1,args=("beijing",))
t2=threading.Thread(target=loop2, args=("tianjin","hangzhou"))
t1.start()
t2.start()
t1.join()
t2.join()
print("all done at ",time.ctime())
if name=="main":
main()
8
运行结果如下：
start at Mon Jan 7 10:06:10 2019
start loop1 at Mon Jan 7 10:06:10 2019
gram1 beijing
start loop2 at Mon Jan 7 10:06:10 2019
gram1 tianjin gram2 hangzhou
end loop2 at Mon Jan 7 10:06:12 2019
end loop1 at Mon Jan 7 10:06:14 2019
all done at Mon Jan 7 10:06:14 2019
守护线程
-如果在程序中将子线程设置成守护线程，则子线程惠子啊主程序结束的时候自动退出
-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
案例5
import time
import threading
import _thread as thread
def fun():
print("start fun")
time.sleep(2)
print("end fun")
print("main thraed")
t1=threading.Thread(target=fun,args=())
将t1设置成守护线程
t1.setDaemon(True)
t1.start()
time.sleep(1)
print("main thread dead")
运行结果如下：
main thraed
start fun
main thread dead
线程常用的属性
-threading.currentThread:返回当前线程呢个变量
-threading.enumerate：返回一个包含正在运行线程的list
-threading.activeCount:返回正在运行的线程的数量
-thr.setName：给线程设置名字
-thr.getName:得到线程的名字
直接继承自thread.Thread
-直接继承Thread
-重写run函数
-类实例可以直接运行
案例6
import time
import threading
类需要继承自threading.Thread
class MyThread(threading.Thread):
def init(self,arg):
super(MyThread, self).init()
self.arg=arg
#必须重写run函数，是真正执行的功能
def run(self):
time.sleep(2)
print("the args for this class is {0}".format(self.arg))
for i in range(5):
t=MyThread(i)
t.start()
t.join()
print("main thread is done")
运行结果如下：
the args for this class is 0
the args for this class is 1
the args for this class is 2
the args for this class is 3
the args for this class is 4
main thread is done
