How to Run Shell Command from Python: Simple Guide

You can run shell commands in Python using the subprocess.run() function, which executes the command and waits for it to finish. Use subprocess.run(['command', 'arg1', 'arg2']) for safe execution without a shell, or add shell=True to run the command through the shell.

Syntax

The basic syntax to run a shell command in Python is using the subprocess.run() function. You pass the command as a list of strings or as a single string with shell=True. The function waits for the command to complete and returns a result object.

• command: List of command and arguments or a string if shell=True.
• shell: Boolean to decide if command runs through the shell.
• capture_output: If True, captures the command output.

python

import subprocess

# Run command without shell
result = subprocess.run(['ls', '-l'], capture_output=True, text=True)

# Run command with shell
result_shell = subprocess.run('ls -l', shell=True, capture_output=True, text=True)

Example

This example shows how to run the echo command to print text from Python and capture its output.

python

import subprocess

result = subprocess.run(['echo', 'Hello from Python'], capture_output=True, text=True)
print('Output:', result.stdout.strip())

Output

Output: Hello from Python

Common Pitfalls

Common mistakes include:

• Using shell=True unnecessarily, which can be a security risk if input is not trusted.
• Passing the command as a string without shell=True, which causes errors.
• Not capturing output and missing command results.

python

import subprocess

# Wrong: string command without shell=True
# subprocess.run('ls -l')  # This will raise an error

# Right: list command without shell
subprocess.run(['ls', '-l'])

# Or string command with shell=True
subprocess.run('ls -l', shell=True)

Quick Reference

Remember these tips when running shell commands from Python:

• Use subprocess.run() for simple command execution.
• Pass commands as a list for safety and avoid shell=True when possible.
• Use capture_output=True and text=True to get command output as a string.
• Be cautious with shell=True to avoid security risks.

Key Takeaways

Use subprocess.run() to execute shell commands safely from Python.

Pass commands as a list of strings to avoid shell injection risks.

Use capture_output=True and text=True to capture and read command output.

Avoid shell=True unless necessary and input is trusted.

Always handle command results to check for success or errors.