How to Detach Background Processes Using Python's `subprocess` Module?

How to Start a Detached Background Process in Python

When converting a shell script to Python, you may encounter the need to start processes in the background that persist even after the script completes. To achieve this, you can utilize Python's subprocess module.

Using subprocess.Popen

The subprocess.Popen function allows you to spawn a new process. To start a process in the background and detach it from the parent process, pass the shell=True and stderr=subprocess.STDOUT arguments to subprocess.Popen:

import subprocess
subprocess.Popen(["command", "arg1", "arg2"], shell=True, stderr=subprocess.STDOUT)

Using the fork() Function

Another option is to use the fork() function to create a child process that runs concurrently with the parent process. However, this method is more advanced and requires careful handling of signals and resources.

Avoiding Blocking

To prevent the parent process from blocking while waiting for the child process to complete, avoid calling the communicate() method on the process object returned by Popen.

Example

To start a process that runs sleep 30 in the background, use the following:

import subprocess
subprocess.Popen(["sleep", "30"])

Clarification

In this context, "background" refers to starting a process that runs independently of the parent process, regardless of whether it's started in a shell background.

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