How Can I Successfully Run Bash Commands from Within a Python Script?

Running Bash Commands in Python

Issue

A Python script fails to run a Bash command using os.system(). The error message indicates that a Python module is not found.

Answer

To resolve this issue and enhance the understanding of running Bash commands in Python, consider the following aspects:

1. Prefer Subprocess Module: Use subprocess.run() or related methods like subprocess.check_call() for better error handling and control. Avoid using os.system().
2. Use text=True: Set text=True to decode standard output and error into Unicode strings.

3. Understand shell=True vs shell=False:

   • shell=True passes a string to the shell for execution.
   • shell=False provides a list of arguments to the operating system, bypassing the shell.

   In general, avoid mixing these options by passing a list of strings with shell=True or a single string with shell=False.

4. Consider Differences Between sh and Bash:

   • Subprocess uses /bin/sh by default unless you specify executable='/bin/bash', which is necessary for Bash-only syntax.

5. Avoid Changing the Parent Environment:

   • A child process cannot change the parent's environment, including setting variables or changing the working directory. Use os.environ[] or pass environment variables to the child process with env=.

6. Avoid Running Python from Python:

   • Consider importing the other Python module and calling its functions directly instead of running the script as a subprocess.

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