How to Execute External Commands Asynchronously from Python

Asynchronous Execution of External Commands from Python

In Python scripting, it is often necessary to invoke external commands that may take an extended amount of time to complete. To ensure that the Python script does not halt while these commands run, asynchronous execution is desired. Previous attempts using os.system() have included the use of & to detach the command from the script's flow, but the suitability of this approach is questionable.

A more effective solution is the subprocess.Popen function. With Popen, you can launch an external command without blocking the Python script's execution. Consider the following example:

from subprocess import Popen
p = Popen(['watch', 'ls']) # something long running
# ... do other stuff while subprocess is running
p.terminate()

This code snippet utilizes Popen to initiate a long-running command (such as 'watch ls'). The Python script can then continue with its own tasks while the external command remains active. When appropriate, the Popen instance can be terminated using the terminate() method.

Moreover, Popen offers additional functionalities such as polling for status, sending input via stdin, and awaiting termination. By leveraging subprocess.Popen, you can seamlessly integrate asynchronous external command execution into your Python scripts.

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