Python Passport

Standard Library

Python subprocess Module

Python External Commands

Python subprocess module runs commands, avoiding shell=True.

What is the subprocess Module?

The subprocess module in Python is a powerful tool that allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes. This module is a more secure and flexible alternative to older functions like os.system() or os.spawn*(). It helps you run shell commands directly from your Python scripts without setting shell=True, which can pose security risks.

Basic Usage of subprocess.run()

The subprocess.run() function is the recommended method for running commands in a subprocess. It returns a CompletedProcess instance, which includes information about the executed command, such as its exit code and output. Here is a basic example:

Handling Errors with subprocess

When a command fails, you might want to handle the error gracefully. By setting the check parameter to True, a CalledProcessError exception is raised if the command exits with a non-zero status:

Capturing Output

To capture the output of a command, use the capture_output=True parameter. This captures standard output and standard error, which you can access via the stdout and stderr attributes of the result:

Passing Input to a Command

If a command requires input, you can pass it using the input parameter. Here is an example that uses the echo command:

Best Practices

  • Avoid using shell=True, as it can introduce security vulnerabilities, especially if you're passing user input.
  • Use subprocess.run() for most use cases. It is simple and returns a CompletedProcess object.
  • Always handle exceptions such as subprocess.CalledProcessError to account for command failures.

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