Python uses multiprocessing to create a process.

Python uses multiprocessing to create a process.

This example describes how to create a process using multiprocessing in Python. Share it with you for your reference. The specific analysis is as follows:

The Process can be created by calling the multiprocessing Process. The following Code creates two processes.

[root@localhost ~]# cat twoproces.py #!/usr/bin/env pythonfrom multiprocessing import Processimport osdef output(): print "My pid is :%d\n" % os.getpid() print "My parent is:%d\n" % os.getppid()def main(): p=Process(target=output)  p.start() print "I am parent %d\n" % os.getpid()if __name__=="__main__": main()

The running result is as follows:

[root@localhost ~]# ./twoproces.py I am parent 7656My pid is :7660My parent is:7656

The mypid value of the following program results will remain unchanged in the two processes.

[root@localhost ~]# cat badprocessID.py #!/usr/bin/env pythonfrom multiprocessing import Processimport osdef output(mypid): print "I am child %d ID :%d\n" % (os.getpid(),mypid)def main(): mypid=os.getpid() p=Process(target=output,args=(mypid,))  print "I am parent %d\n" % os.getpid() p.start()if __name__=="__main__": main()

Mypid has not been reset with the sub-process, so the mypid does not change during running.

The following code creates a process chain for sub-processes.

[root@localhost ~]# cat simplechina.py #!/usr/bin/env pythonimport osfrom multiprocessing import Processdef output(howmany,childpid): info = (howmany,os.getpid(),os.getppid(),childpid) print "i:%d process ID:%d parent ID%d child ID %d\n" % infodef chain(howmany): howmany = howmany-1 if howmany > 0: p = Process(target=chain,args=(howmany,))  p.start() output(howmany,p.pid)def main(): childpid = 0 howmany=6 p = Process(target=chain,args=(howmany,)) p.start()if __name__=="__main__": main()

With the main Process using Process to create A sub-Process, and sub-Process and then create A sub-Process (that is, A-> B-> C-D), and so on, know that howmany is less than 0 to end. The result of running 1 is as follows:

[root@localhost ~]# ./simplechina.py i:5 process ID:13581 parent ID13580 child ID 13582i:4 process ID:13582 parent ID13581 child ID 13583i:3 process ID:13583 parent ID13582 child ID 13584i:2 process ID:13584 parent ID13583 child ID 13585i:1 process ID:13585 parent ID13584 child ID 13586

How to create a process fan:
A
/\
B C
Create the simplefan. py file with the following code:

[root@localhost ~]# cat simplefan.py #!/usr/bin/env pythonimport osfrom multiprocessing import Processdef output(howmany,childpid): info = (howmany,os.getpid(),os.getppid(),childpid) print "i:%d process ID:%d parent ID%d child ID %d\n" % infodef fan(i): output(i,os.getpid())def main(): pList=[] for i in range(6): p = Process(target=fan,args=(i,)) pList.append(p) for p in pList: p.start() for p in pList: p.join()if __name__=="__main__": main()

The running result is as follows:

[root@localhost ~]# ./simplefan.py i:0 process ID:13594 parent ID13593 child ID 13594i:2 process ID:13596 parent ID13593 child ID 13596i:3 process ID:13597 parent ID13593 child ID 13597i:1 process ID:13595 parent ID13593 child ID 13595i:4 process ID:13598 parent ID13593 child ID 13598i:5 process ID:13599 parent ID13593 child ID 13599

Except for the process whose ID is 13593, the parent process of other processes is 13593.
The parent process ends with all sub-processes, such as the join method.

I hope this article will help you with Python programming.