Are you looking for ways to run shell commands in your Python script? If so, then Python’s subprocess module is a powerful tool you should explore. This module provides several functions for executing shell commands and managing input/output streams. Two of the most commonly used functions are check_call and check_output.
But what sets check_call apart from check_output? Well, check_call runs a command and waits for the process to complete before returning the status code. On the other hand, check_output runs a command and captures its output. This means that check_output returns both the output and status code of the process.
If you’re wondering which function to use, it depends on your needs. If you only need to check if a process was successful, then check_call may be enough. However, if you also need to retrieve the output of the process, then check_output will be more useful.
In this article, we’ll take a closer look at these two functions and explore their different use cases. Whether you’re a beginner or an experienced Python developer, you’ll surely find something valuable from reading this article.
So, without further ado, let’s dive into the world of Python subprocess and learn how to effectively use check_call and check_output. By the end of this article, you’ll have a better grasp of these two functions and be able to use them in your own projects.
“Python Subprocess .Check_call Vs .Check_output” ~ bbaz
Introduction
Python’s subprocess module is used to create new processes and interact with them. It provides a simple interface to run external commands from within Python. The module offers various methods such as Popen, call, check_call, check_output, and many others. In this article, we will focus on check_call and check_output methods.
What is check_call?
The check_call method is used to execute an external command and wait until the process finishes. If the process returns a non-zero exit status, then it raises a CalledProcessError exception. We can use this method for simple command-line interactions where we don’t need to capture the output of the command.
What is check_output?
The check_output method is used to execute an external command and capture its output. It returns the output of the command as a byte string. If the process returns a non-zero exit status, then it raises a CalledProcessError exception.
Comparison Table
| Method | Used For | Output | Raise Exception |
|---|---|---|---|
| check_call | Execute a command and wait for it to finish | No output captured | Non-zero exit status |
| check_output | Execute a command and capture its output | Output captured as byte string | Non-zero exit status |
Example for check_call
Let’s consider an example where we want to execute the ‘ls’ command and list all the files in a directory.
import subprocesstry: subprocess.check_call(['ls', '-l', '/path/to/directory'])except subprocess.CalledProcessError as e: print(fCommand '{e.cmd}' returned non-zero exit status {e.returncode})Example for check_output
Let’s consider an example where we want to execute the ‘ls’ command and capture its output.
import subprocesstry: output = subprocess.check_output(['ls', '-l', '/path/to/directory']) print(output.decode('utf-8'))except subprocess.CalledProcessError as e: print(fCommand '{e.cmd}' returned non-zero exit status {e.returncode})Opinion on using check_call and check_output
Both check_call and check_output methods are used for executing external commands, but the main difference is that check_output captures the output of the command while check_call doesn’t. We should use check_call when we don’t need to capture the output of the command and just need to know if it executed successfully or not. On the other hand, we should use check_output when we need to capture the output of the command and process it further. Therefore, the usage of these methods depends on our requirements.
Conclusion
In this article, we have learned about the check_call and check_output methods in Python’s subprocess module. We compared them based on their usage, output, and exception handling. We also provided examples for both methods and gave our opinion on when to use each method. It’s important to understand the differences between these methods and choose the appropriate one based on our requirements.
Dear visitors,
Thank you for taking the time to read this article on differentiating check_call and check_output in Python subprocess. We hope that you found it informative and helpful in your coding endeavors.
As we discussed in the article, check_call and check_output are two useful functions in the subprocess module of Python. While they may appear similar at first glance, there are important differences between them that can impact their usage in your code.
By understanding the differences between check_call and check_output, you can make more informed decisions about which function is best suited for your specific needs. For example, check_call is typically used when you want to execute a command and check that it returns a zero status code, while check_output is used when you want to run a command and capture its output to use in further processing.
We encourage you to continue exploring the subprocess module and other Python libraries to expand your knowledge and improve your coding skills. Thank you again for visiting our blog, and we look forward to sharing more valuable insights with you in the future.
Here are some common questions that people ask about differentiating check_call and check_output in Python subprocess:
- What is the difference between check_call and check_output in Python subprocess?
- How do I choose between check_call and check_output in my Python script?
- Can I use check_output instead of check_call or vice versa?
Here are some answers to these questions:
- What is the difference between check_call and check_output in Python subprocess?
- How do I choose between check_call and check_output in my Python script?
- Can I use check_output instead of check_call or vice versa?
The main difference between check_call and check_output is how they handle the output of the command being executed. check_call will simply execute the command and return a zero exit code if the command was successful. check_output, on the other hand, will capture the output of the command and return it as a byte string. If the command fails, it will raise a CalledProcessError exception.
If you don’t need to capture the output of the command being executed, you should use check_call. If you need to capture the output for further processing, you should use check_output.
You can use check_output instead of check_call if you don’t need to capture the output of the command. However, you cannot use check_call instead of check_output if you need to capture the output.
