Python has gone to excellent heights. That’s not surprising. But there are situations where we need to use the system commands instead of the pure Pythonic way.
Python is compatible with this, either. You can run almost any system command without opening a terminal. There are inbuilt options in Python to do this.
When you can programmatically do shell commands, you can do more with the flexibility of Python and the intricacy of your operating system.
1. Using os.system
One of the simplest ways to run a command in Python is by using the
os.system function. This method allows passing bash commands and arguments directly to the system’s shell. For instance:
os.system("some_command < input_file | another_command > output_file")
os.system is convenient for executing multiple commands, setting up pipes, and input/output redirection; it requires manual handling of shell characters like spaces. However, it also provides the flexibility to run shell commands directly.
2. Embracing subprocess.run (Python 3.5+)
For the most flexibility and control over bash command execution, Python 3.5 introduced the
subprocess.run function. It not only captures the return code but also provides access to the output, error, and other process-related information. Let’s see an example:
result = subprocess.run(
["echo", "Hello", "World"],
In this example, we use
subprocess.run to execute the command
echo Hello World and capture the output using the
capture_output=True argument. The
text=True argument decodes the output as text, and we print the result.
The official documentation provides in-depth information on the subprocess module, its various functions, and usage examples.
This tutorial by Real Python provides a comprehensive overview of the subprocess module with practical examples and best practices.
3. Leveraging os.popen
An alternative to
os.popen, which not only executes commands but also provides a file-like object for accessing standard input/output. By passing the command as a string or a list, you can avoid the hassle of escaping characters. Consider the following example:
output = os.popen("ls -l").read()
In this case, we use
os.popen to run the
ls -l command and store the output in the
4. Harnessing the Power of subprocess.Popen
For more advanced command execution and greater flexibility, the
subprocess.Popen class is a recommended choice. This comprehensive class replaces
os.popen and provides various options for controlling input/output streams, handling errors, and more. Let’s see an example:
process = subprocess.Popen(
"echo Hello World",
output = process.stdout.read()
In this example, we create a
subprocess.Popen instance to execute the command
echo Hello World. The
shell=True argument enables the use of shell syntax. We capture the output using
process.stdout.read() and print it.
5. Simplifying with subprocess.call
If you only need the return code of a command and don’t require complex I/O handling,
subprocess.call provides a simplified alternative. It waits for the command to complete and returns the return code. Consider this example:
return_code = subprocess.call("echo Hello World", shell=True)
Here, we execute the command
echo Hello World and store the return code in the
Less recommended methods.
While the methods described above, such as
subprocess.Popen, cover most common use cases for executing commands in Python, there are alternatives available that closely resemble their counterparts in the C language. These alternatives include
os.spawn. However, it is generally not recommended to use these methods directly in Python due to their complexity and potential pitfalls.
In this guide, we explored various methods for running commands in Python, optimizing for the keyword “python run command”. From the straightforward
os.system to the powerful
subprocess.run, Python provides a range of options to execute external programs seamlessly. By understanding these techniques and following best practices, you can harness the full potential of Python for executing commands and automating system tasks with confidence and security.
When executing commands with user input or any untrusted parts, it is crucial to consider security implications. Ensure that all inputs are properly validated and sanitized to prevent any potential command injection vulnerabilities. It is recommended to use constant values or thoroughly validate user input before using it in command execution.
An informative tutorial by GeeksforGeeks that covers different methods to execute shell commands in Python, including os.system, os.popen, and subprocess.Popen, and subprocess.run.
Now, armed with this knowledge, you can confidently leverage Python’s command execution capabilities to streamline your development workflow and accomplish tasks that extend beyond the confines of your Python code. Happy coding!