How to Run Detached Background Processes in Python?

How to Launch Detached Background Processes in Python

Running processes in the background is crucial for long-running or non-interactive tasks in Python. The original shell script utilized the "&" operator to launch processes that would continue executing even after the script's completion. In Python, achieving a similar outcome requires understanding daemons and the appropriate modules for process management.

Using the subprocess Module

The recommended approach for handling background processes in Python is the subprocess module. While jkp's solution is functional, the subprocess module offers more flexibility and aligns with current documentation recommendations.

For simple commands, the usage of the subprocess module mimics the "&" operator in the shell script. Consider the following example to start a new process that deletes a file in the background:

import subprocess
subprocess.Popen(["rm", "-r", "some.file"])

Notes on Execution

Calling the .communicate() method on the returned object from Popen will block the main process until the background process completes. If you intend for the background process to remain detached, avoid calling .communicate(). Here's an illustration of this behavior:

import subprocess
ls_output = subprocess.Popen(["sleep", "30"])
ls_output.communicate()  # Blocks for 30 seconds

For more advanced use cases, the subprocess documentation provides comprehensive guidance on process management, including input/output redirection and error handling.

It's worth clarifying that "background" in this context refers to the shell concept of running a process without blocking its execution, rather than the true concept of a daemon process in the operating system sense.

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