11-2 Python多线程threading

分进程设置
工具： threading包

1  先写需要分进程运行的函数或者类  
def maigic():
    pass    
    
2  实例化threading，得到新的进程  
threadone = threading.Thread(target=maigic)  
此时还可以接受arg参数   

import threading
import time

def get_html():
    print("get_html is start ")
    time.sleep(3)
    print("get_html is end")

def get_url():
    print("get_url is start")
    time.sleep(2)
    print("get_url is end")

thread1 = threading.Thread(target=get_html)
thread2 = threading.Thread(target=get_url)

start_time = time.time()
print("start time is {}".format(start_time))
thread1.start()
thread2.start()

end_time = time.time()
print("end time is {}".format(end_time-start_time))

>>> 

start time is 1532486991.7209127
get_html is start 
get_url is start
end time is 0.0004737377166748047
get_url is end
get_html is end

此时整个程序存在三个进程，
1 主进程：程序运行
2 进程1 ： thread1
3 进程2 ： thread2

三个进程属于并发的，主程序会等到其余两个进程结束后，主程序才会结束
但是主程序是执行完所有语句然后等待其余进程的结束，而不是停在进程语句哪里等待

此时可以设置守护进程--优先级在主进程之下，主进程可以kill掉守护进程    
thread1.setDaemon(True)  #将thread2设为守护进程   
thread1.join()           # 等待进程结束

import threading
import time


def get_html():
    print("get_html is start ")
    time.sleep(3)
    print("get_html is end")

def get_url():
    print("get_url is start")
    time.sleep(2)
    print("get_url is end")

thread1 = threading.Thread(target=get_html)
thread2 = threading.Thread(target=get_url)

thread1.setDaemon(True)
thread2.setDaemon(True)          # 将thread2设为守护进程--优先级在主进程之下，主进程可以kill掉守护进程
start_time = time.time()
print("start time is {}".format(start_time))
thread1.start()
thread2.start()

thread1.join()                # 等待进程结束
thread2.join()
end_time = time.time()
print("end time is {}".format(end_time-start_time))

>>> 

start time is 1532486991.7209127
get_html is start 
get_url is start
get_url is end
get_html is end
end time is 0.0004737377166748047

有了守护进程之后，主程序就会在自身结束后，（不管守护进程还是不是在运行）kill守护进程
但是有了 :

thread1.join()     # 等待进程结束
thread2.join() 

主程序就会停在join哪里，等待结束后，再继续执行

改进把变成类，自定义类继承threading.Thread 类
此时需要重载run方法 ， run方法就是运行逻辑

import threading
import time

class Thread_case(threading.Thread):
    def __init__(self,name,time):
        self.mytime = time
        self.myname = name
        super().__init__(name=name)

    def run(self):
        print("{name} is start ".format(name=self.myname))
        time.sleep(self.mytime)
        print("{name} is end".format(name=self.myname))


thread1 = Thread_case("get_url",3)
thread2 = Thread_case("get_html",2)
thread1.setDaemon(True)
start_time = time.time()
print("start time is {}".format(start_time))
thread1.start()
thread2.start()


# thread1.join()                # 等待进程结束
# thread2.join()
end_time = time.time()
print("end time is {}".format(end_time-start_time))

>>>  
start time is 1532496367.0786047
get_url is start 
get_html is start 
end time is 0.0009756088256835938
get_html is end