Running Python Scripts from Other Scripts with Command-Line Arguments

Python provides several ways to run a script from another script while passing command-line arguments. This can be useful for tasks such as automating workflows, testing, or reusing code. In this tutorial, we will explore the different methods for achieving this.

Using the Subprocess Module

The subprocess module is the recommended way to run external commands and scripts in Python. It provides a flexible and powerful interface for managing processes. To use it, you can import the module and create a Popen object with the command you want to execute.

import subprocess

# Define the script name and argument
script_name = "script2.py"
argument = 1

# Construct the command string
command = f"python {script_name} {argument}"

# Run the command using subprocess
subprocess.run(command, shell=True)

Note that in this example, we use shell=True to execute the command through the shell. This allows us to pass a single string with the command and arguments, but it can also introduce security risks if you’re not careful.

Using os.system

The os.system function is another way to run external commands, but it’s less flexible than subprocess. It’s generally recommended to use subprocess instead of os.system, as it provides more features and better error handling.

import os

# Define the script name and argument
script_name = "script2.py"
argument = 1

# Construct the command string
command = f"python {script_name} {argument}"

# Run the command using os.system
os.system(command)

Importing and Calling Functions Directly

If you have control over both scripts, it’s often better to import the second script as a module and call its functions directly. This approach avoids the overhead of creating a new process and allows for more flexible communication between the scripts.

import script2

# Define the argument
argument = 1

# Call the function from script2.py
script2.some_function(argument)

Modifying sys.argv

In some cases, you might need to modify sys.argv to pass arguments to a script without changing its source code. You can use a context manager to temporarily change sys.argv and restore it later.

import contextlib
import sys

@contextlib.contextmanager
def redirect_argv(argument):
    original_argv = sys.argv[:]
    sys.argv = [str(argument)]
    yield
    sys.argv = original_argv

with redirect_argv(1):
    # Run the script or call its functions here
    pass

Best Practices and Security Considerations

When running scripts from other scripts, keep in mind the following best practices and security considerations:

• Avoid using shell=True with untrusted input to prevent shell injection attacks.
• Use subprocess.run instead of os.system for better error handling and flexibility.
• Consider importing and calling functions directly if you have control over both scripts.
• Be cautious when modifying sys.argv, as it can affect the behavior of other parts of your program.

By following these guidelines and examples, you should be able to run Python scripts from other scripts while passing command-line arguments effectively and securely.