How to Execute Shell Commands Asynchronously in Python

Run External Commands Asynchronously with Python

As a Python developer, you may encounter scenarios where you need to execute shell commands asynchronously, allowing your script to continue running uninterrupted. While the documentation provides numerous ways to call external commands, determining the most appropriate approach can be challenging.

os.system() and &

In your experimentation, you discovered that using os.system() with & at the command's end allows asynchronous execution. This method is indeed effective for initiating a command without waiting for its completion. However, there are some drawbacks to consider.

subprocess.Popen as the Ideal Solution

For asynchronous command execution, subprocess.Popen is a more comprehensive and recommended approach. It provides precise control and a versatile interface for managing external processes.

<code class="python">from subprocess import Popen
p = Popen(['watch', 'ls'])  # Example command to run</code>

Benefits of Popen:

• Asynchronous execution: Allows your script to continue running while the command is executing.
• Monitoring capabilities: You can poll() the Popen instance to check if the command is still running.
• Communication: Use communicate() to send data to the command's stdin or receive output from its stdout/stderr.
• Termination: Gracefully terminate the process using terminate().

Conclusion:

While os.system() can superficially achieve asynchronous execution, subprocess.Popen offers a more robust and feature-rich solution for managing external commands asynchronously. Its versatility and monitoring capabilities make it the preferred choice for controlling external processes in Python.

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