Get pid
The current process point of view
os.getpid () Gets the current process pid
os.getppid () # get the parent process pid of the current process
The child objects .pid # obtain a child process pid the current process
Zombie process and orphaned
Zombie process (harmful): The exit (after) still have pid, did not immediately disappear, the parent process to wait for treatment
If you have a large number of zombie process, not only the process ID will cause the system can not produce a new process, this process should avoid harm
Orphaned (harmless): The parent process exits one or more sub-process is still run by the init process to complete their processing status
init process handles all his rehabilitation work.
Daemon
- Broke into the master daemon process
- Daemon will terminate after the end of the main process code execution.
- Within daemon can no longer turn a child process, otherwise an exception is thrown.
Between processes are independent of each other, the end of the main process code to run, stop the daemon
def task(x): print(f'{x} start') time.sleep(2) print(f'{x} end') if __name__ == '__main__': p=Process(target=task,args=('sb',)) p.daemon = True ##一定要在p.start()前设置,设置p为守护进程,禁止p创建子进程,并且父进程代码执行结束,p即终止运行 p.start() print('主')
Object .join ()
A request to the operating system, and then inform the operating system do not need the id p is occupied, can be recovered
But will remain a pid, zombie
from multiprocessing import Process
import time,os
def task():
print('%s is running' %os.getpid())
time.sleep(3)
if __name__ == '__main__':
p=Process(target=task)
p.start()
p.join() # 等待进程p结束后，join函数内部会发送系统调用wait，去告诉操作系统回收掉进程p的id号
print(p.pid) #此时能看到子进程p的id号
print('主'）is_alive()
Determine whether the process is already running End
terminate
Direct terminate processes running
Analog grab votes applet
Multiple processes to share a file
When the database file, analog to grab votes
from multiprocessing import Process
import json,time,os
def search():
time.sleep(1) # 模拟网络io
with open('db.txt',mode='rt',encoding='utf-8') as f:
res = json.load(f)
print(f'还剩{res["count"]}')
def get():
with open('db.txt',mode='rt',encoding='utf-8') as f:
res = json.load(f)
# print(f'还剩{res["count"]}')
# time.sleep(1) # 模拟网络io
if res['count'] > 0:
res['count'] -= 1
with open('db.txt',mode='wt',encoding='utf-8') as f:
json.dump(res,f)
print(f'进程{os.getpid()} 抢票成功')
time.sleep(1.5) # 模 拟网络io
else:
print('票已经售空啦!!!!!!!!!!!')
def task():
search()
get()
if __name__ == '__main__':
for i in range(15):
p = Process(target=task)
p.start()
# p.join()
# 为了保证数据的安全,要牺牲掉效率.