Python的并发并行[3] -> 进程[1] -> 多进程的基本使用

多进程的基本使用

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1 subprocess 常用函数示例

首先定义一个子进程调用的程序，用于打印一个输出语句，并获取命令行参数

 import sys
 print('Called_Function.py called, Hello world.')
 try:
     print('Got para', sys.argv[1:])
 except:
     pass

再定义主函数，即父进程，分别测试 run() / call() / check_call() / getstatusoutput() / getoutput() / ckeck_output函数。

 import subprocess
 
 # subprocess.run()
 print('---------subprocess.run------------')
 re = subprocess.run(['python', 'Called_Function.py', 'para_1', 'para_2'])
 print('subprocess.run() test returns obj:', re)
 print('Return code is: {0}, stdout is: {1}, stderr is: {2}'.format(re.returncode, re.stdout, re.stderr))
 
 # subprocess.call()
 print('\n---------subprocess.call------------')
 print('subprocess.call() test returns code:', subprocess.call(['python', 'Called_Function.py', 'para_1', 'para_2']))
 
 # subprocess.ckeck_call()
 print('\n---------subprocess.check_call------------')
 try:
     print('subprocess.check_call() test returns code:', subprocess.check_call(['python', 'Called_Function.py']))
 except subprocess.CalledProcessError:
     print('Failed to call.')
 
 # subprocess.getstatusoutput()
 print('\n---------subprocess.getstatusoutput------------')
 print('subprocess.getstatusoutput() test returns:', subprocess.getstatusoutput(['python', 'Called_Function.py']))
 
 # subprocess.getoutput()
 print('\n---------subprocess.getstatusoutput------------')
 print('subprocess.getoutput() test returns:', subprocess.getoutput(['python', 'Called_Function.py']))
 
 # subprocess.check_output()
 print('\n---------subprocess.check_output------------')
 print('subprocess.check_output() test returns:', subprocess.check_output(['python', 'Called_Function.py']))

2 利用Popen类与子进程交互

首先定义一个子进程调用的函数，函数中需求一个输入

 x = input('Please input something.')
 print(x, 'Hello World!')
 # Raise an error
 print(y)

再定义父进程的函数

 import subprocess
 
 prcs = subprocess.Popen(['python', 'Called_Function_Popen.py'],
                         stdout=subprocess.PIPE,
                         stdin=subprocess.PIPE,
                         stderr=subprocess.PIPE,
                         universal_newlines=True,
                         shell=True)
 
 print('subprocess pid:', prcs.pid)
 
 re = prcs.communicate('These string are from stdin')
 print('\nSTDOUT:', re[0])
 print('\nSTDERR:', re[1])
 if prcs.poll():
     print('\nThe subprocess has been done')

相关阅读

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1. subprocess 模块