In today’s fast-paced world, automation and efficiency are key to staying ahead of the curve. One such area where automation plays a crucial role is running system commands through programming languages such as Python. This article will guide you through the process of running system commands using Python, diving into the underlying code and shedding light on relevant libraries and functions.
To start off, Python offers a couple of ways to execute system commands. One popular option is to use the os library, while another efficient choice includes the subprocess module. In this article, we will focus on the subprocess module, as it provides more flexibility and control over the execution of external commands.
Contents
Python’s Subprocess Module
- Python’s subprocess module allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes.
- To get started with the subprocess module, you’ll first need to import it with the following command:
import subprocess.
Now that we’ve imported the subprocess module, let’s explore its primary function: run(). This function takes a variety of arguments, the most basic of which is a list specifying the command you’d like to execute and any additional arguments required.
Running System Commands with Subprocess
Let’s walk through an example. If you’d like to create a new directory called “example_directory” using the system command “mkdir”, you would run the following code:
import subprocess command = ["mkdir", "example_directory"] result = subprocess.run(command)
In this example, the run() function accepts the list command, which contains the system command “mkdir” and the argument for the desired directory name. The function then returns a subprocess.CompletedProcess object, containing information such as the return code and any output or error messages generated by the command.
For more control over the executed command, additional arguments can be passed to the run() function, such as stdout and stderr. By default, these are set to None, meaning the output and error messages are not captured. However, setting them to subprocess.PIPE allows you to capture these messages for further processing.
import subprocess
command = ["mkdir", "example_directory"]
result = subprocess.run(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
print(f"Output: {result.stdout}")
print(f"Error: {result.stderr}")
print(f"Return Code: {result.returncode}")
Useful Functions in the Subprocess Module
In addition to the run() function, the subprocess module contains several other helpful functions, including:
- call(): This function works similar to run(), but only returns the return code of the executed command.
- check_call(): Similar to call(), this function throws a CalledProcessError exception if the command returns a non-zero exit code.
- check_output(): This function returns the output of the command, but throws a CalledProcessError exception if the command returns a non-zero exit code.
- Popen(): This class provides more advanced functionality, including the ability to interact with the executed process via its input, output, and error streams.
Other Libraries for Running System Commands
Besides the subprocess module, there are other libraries available for running system commands in Python:
- os: The os module also provides a means to execute system commands using functions such as os.system() and os.popen(), but with less flexibility and control compared to the subprocess module.
- sh: This third-party library offers a more Pythonic approach to executing system commands, allowing for easier interaction with command line tools.
In conclusion, running system commands in Python is a crucial skill for automation and efficiency. The subprocess module stands out as the most versatile and powerful option, providing users with many options for executing and controlling external commands. With this understanding, you can now harness the power of Python to streamline your processes and boost your productivity.
