How to Call a Python Script from Bash

Integrating Python scripts with Bash is a common requirement for automation, data processing, and system administration tasks. Whether you're a developer or a DevOps engineer, knowing how to execute Python code from the command line efficiently can save time and streamline workflows.

Basic Method: Using the Python Interpreter

The simplest way to run a Python script from Bash is by invoking the Python interpreter directly. Here's how:

python3 script_name.py

Replace script_name.py with your Python file's name. If you're using Python 2 (though it's outdated), replace python3 with python.

Passing Arguments to the Script

You can pass command-line arguments to your Python script like this:

python3 script_name.py arg1 arg2 arg3

In your Python script, use the sys.argv list from the sys module to access these arguments:

import sys

if __name__ == "__main__":
    print("Arguments passed:", sys.argv)

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Using Shebang for Direct Execution

For a more seamless experience, add a shebang line at the top of your Python script to specify the interpreter:

#!/usr/bin/env python3

Then, make the script executable using chmod:

chmod +x script_name.py

Now, you can run the script directly:

./script_name.py

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Advanced: Capturing Output in Bash

You can capture the output of a Python script in a Bash variable for further processing:

output=$(python3 script_name.py)
echo "Python script output: $output"

Error Handling

Check the exit status of your Python script in Bash to handle errors:

if python3 script_name.py; then
    echo "Script executed successfully"
else
    echo "Script failed"
fi

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Using Subprocess Module for Complex Integrations

For more complex scenarios, the subprocess module in Python allows you to call Bash commands from Python and vice versa. Here's an example:

import subprocess

result = subprocess.run(['ls', '-l'], stdout=subprocess.PIPE)
print(result.stdout.decode('utf-8'))

This runs the ls -l command in Bash and captures its output in Python.

Summary: Learn how to execute Python scripts from Bash using basic commands, shebang, and advanced techniques like output capture and error handling. The subprocess module is widely used for bidirectional integration.

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