多线程、进程

import threading,time
def run():
   time.sleep(3) #干活需要3s
   print('哈哈哈')
# for i in range(5): #串行
#  run()
# for i in range(5):
#  t = threading.Thread(target=run) #实例化了一个线程
#  t.start()
#多线程， 就是N个线程一起在干活




#1、串行
# start_time = time.time()
# for k,v in urls.items():
#  down_html(k,v)
# end_time = time.time()
# run_time = end_time - start_time
# print('下载总共花了xxx时间',run_time)


#2、并行
urls = {
   'besttest':'http://www.besttest.cn',
   'niuniu':'http://www.nnzhp.cn',
   'dsx':'http://www.imdsx.cn',
   'cc':'http://www.cc-na.cn'
}
import requests,time
data= {}
def down_html(file_name,url):
   start_time = time.time()
   res = requests.get(url).content
   open(file_name+'.html','wb').write(res)
   end_time = time.time()
   run_time = end_time-start_time
   data[url] = run_time
threads = []
start_time = time.time()
for k,v in  urls.items():   #5次
   t = threading.Thread(target=down_html,args=(k,v)) #多线程的函数如果传参的话，必须得用args
   t.start()
   threads.append(t)
#6个线程
#进程里面默认有一个线程，这个线程叫做主线程
for t in threads:
   t.join()

print(data)
end_time = time.time()
run_time = end_time - start_time
print('下载总共花了xxx时间',run_time)



多线程等待

import threading,time
def run():
   # time.sleep(3)
   print('哈哈哈')
start_time = time.time()
threads = []  #存放启动的5个线程
for i in range(5):
   t = threading.Thread(target=run)
   t.start()#
   threads.append(t)

for lyl in threads:  #主线程循环等待5个子线程执行结束
   lyl.join()
end_time = time.time()
print('run_time..',end_time-start_time)


多进程

import multiprocessing,threading

def my():
   print('哈哈哈')

def run(num):
   for i in range(num):
      t = threading.Thread(target=my)
      t.start()
if __name__ == '__main__':
   for i in range(5):
      p = multiprocessing.Process(target=run,args=(6,))  #启动一个进程
      p.start()

守护线程

import threading,time

def run():
   time.sleep(3)
   print('哈哈哈')

for i in range(50):
   t = threading.Thread(target=run)
   t.setDaemon(True) #把子线程设置成为守护线程
   t.start()

print('Done,运行完成。')
time.sleep(3)