How to create a process using multiprocessing in Python

How to create a process using multiprocessing in Python

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.

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[Root @ localhost ~] # Cat twoproces. py #! /Usr/bin/env python From multiprocessing import Process Import OS Def 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:

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

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

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[Root @ localhost ~] # Cat badprocessID. py #! /Usr/bin/env python From multiprocessing import Process Import OS Def 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.

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[Root @ localhost ~] # Cat simplechina. py #! /Usr/bin/env python Import OS From multiprocessing import Process Def output (howworkflow, childpid ): Info = (howmany, OS. getpid (), OS. getppid (), childpid) Print "I: % d process ID: % d parent ID % d child ID % d \ n" % info Def chain (howchain ): Howmany = howmany-1 If howtasks> 0: P = Process (target = chain, args = (howmany ,)) P. start () Output (howmany, p. pid) Def main (): Childpid = 0 Howtasks = 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:

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[Root @ localhost ~] #./Simplechina. py I: 5 process ID: 13581 parent ID13580 child ID 13582 I: 4 process ID: 13582 parent ID13581 child ID 13583 I: 3 process ID: 13583 parent ID13582 child ID 13584 I: 2 process ID: 13584 parent ID13583 child ID 13585 I: 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:

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[Root @ localhost ~] # Cat simplefan. py #! /Usr/bin/env python Import OS From multiprocessing import Process Def output (howworkflow, childpid ): Info = (howmany, OS. getpid (), OS. getppid (), childpid) Print "I: % d process ID: % d parent ID % d child ID % d \ n" % info Def 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:

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[Root @ localhost ~] #./Simplefan. py I: 0 process ID: 13594 parent ID13593 child ID 13594 I: 2 process ID: 13596 parent ID13593 child ID 13596 I: 3 process ID: 13597 parent ID13593 child ID 13597 I: 1 process ID: 13595 parent ID13593 child ID 13595 I: 4 process ID: 13598 parent ID13593 child ID 13598 I: 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.