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This article mainly explains "how to use subprocess in python". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn how to use subprocess in python.

1, subprocess this module to generate child processes, and can be connected to the child process's standard input, output, errors, but also can get the return value of the child process.

2. Subprocess provides two ways to call subroutines.

Instance # coding:utf-8import os# popen returns a file object, like the open operation, f = os.popen (r "ls", "r") l = f.read () print (l) f.close ()

Expansion of Python subprocess knowledge points

The purpose of using the subprocess module is to replace some old modules and methods such as os.system.

When we run python, we are all creating and running a process. Like the Linux process, a process can fork a child process and have that child process exec another program. In Python, we use the subprocess package in the standard library to fork a child process and run an external program.

Several functions for creating child processes are defined in the subprocess package, and these functions create child processes in different ways, so we can choose one of them to use as needed. In addition, subprocess provides tools for managing standard streams (standard stream) and pipes (pipe) to use text communication between processes.

Import module

> import subprocess

Command executes call ()

Execute the command provided by the parameter and run the command with the array as a parameter. Its function is similar to os.system (cmd).

> subprocess.call (['ls','-l')

The parameter shell defaults to False.

When shell is set to True, you can pass the string directly:

> subprocess.call ('ls-Lindsay Magnum shellflower True)

Get the returned result check_output ()

Call () does not return the displayed result, and you can use check_ouput () to get the returned result:

> result = subprocess.check_output (['ls','-l'], shell=True) > result.decode (' utf-8')

The process creates and manages Popen classes

Subprocess.popen replaces os.popen. You can create a Popen class to create processes and perform complex interactions.

Create a child process that does not wait

Import subprocesschild = subprocess.Popen (['ping','-c','4','www.baidu.com']) print (' Finished')

Add child process wait

Import subprocesschild = subprocess.Popen (['ping','-c','4','www.baidu.com']) child.wait () # wait for the child process to end print (' Finished')

With wait () added, the main process waits for the child process to finish before executing the following statement.

Child process text flow control

Standard output redirection:

Import subprocesschild = subprocess.Popen (['ls','-l'], stdout=subprocess.PIPE) # directs standard output to subprocess.PIPEprint (child.stdout.read ())

Use stdin with it:

Import subprocesschild1 = subprocess.Popen (['cat','/etc/passwd'], stdout=subprocess.PIPE) child2 = subprocess.Popen ([' grep','root'], stdin=child1.stdout,stdout=subprocess.PIPE) print child2.communicate () Thank you for your reading, the above is the content of "how to use subprocess in python". After the study of this article, I believe you have a deeper understanding of how to use subprocess in python, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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