Скачать или смотреть How to Enforce Strict Command Line Arguments with argparse in Python

Learn how to prevent unintended command line arguments in Python using `argparse` by enforcing strict argument rules with helpful tips.
---
This video is based on the question https://stackoverflow.com/q/64459855/ asked by the user 'pjk' ( https://stackoverflow.com/u/8858658/ ) and on the answer https://stackoverflow.com/a/64460268/ provided by the user 'python_user' ( https://stackoverflow.com/u/12502959/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Command line args accepting -SS also where as expected is -S using argparse

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Enforce Strict Command Line Arguments with argparse in Python

When working with command line arguments in Python, using the argparse module is a common practice. It allows developers to create user-friendly command-line interfaces for their programs. However, a frequent challenge arises: how to handle invalid command line arguments, particularly when users combine flags incorrectly. For example, suppose you defined a command line argument -S but want to disallow similar, unintended variations like -SS—how can you enforce this strictly? Today, we’ll answer that question, and you’ll learn how to prevent undesired command line behaviors effectively.

The Issue at Hand

Consider the following code snippet that utilizes argparse to define a command line option:

[[See Video to Reveal this Text or Code Snippet]]

In this snippet, -S is a flag that users can enable to save data to a directory. However, if a user mistakenly enters -SS, Python does not throw an error, which can lead to confusion or unexpected behavior in your program. Thus, you're left wondering: How can I enforce stricter argument validation to catch this kind of error?

The Solution: Enabling Strict Argument Parsing

To solve this problem, you just need to turn on strict argument validation in argparse. The solution is straightforward: you should use the parameter allow_abbrev=False in the ArgumentParser.

Step-by-Step Implementation

Import the argparse Module:
Just like before, start by importing argparse.

[[See Video to Reveal this Text or Code Snippet]]

Create an Argument Parser with Abbreviation Disabled:
When you instantiate ArgumentParser, set allow_abbrev to False. This will enforce that users can only use the full argument names.

[[See Video to Reveal this Text or Code Snippet]]

Define Your Argument:
Add the desired argument as before.

[[See Video to Reveal this Text or Code Snippet]]

Parse the Arguments:
Finally, use the parse_args() method to handle user inputs.

[[See Video to Reveal this Text or Code Snippet]]

Full Example Code

Putting it all together, here’s the complete code snippet:

[[See Video to Reveal this Text or Code Snippet]]

Testing the Implementation

Now, let’s see how the program behaves with this implementation. If you use the commands below:

[[See Video to Reveal this Text or Code Snippet]]

You will receive output similar to:

[[See Video to Reveal this Text or Code Snippet]]

This outcome indicates that the program correctly identifies and flags the unintended -SS argument, showing an error message.

Conclusion

By setting allow_abbrev=False in your argparse.ArgumentParser, you can ensure that your command line arguments are strictly validated, which prevents accidental uses of incorrect flag combinations. This small change can significantly improve the robustness of your command line application and enhance the user experience by providing clear feedback on incorrect usage. Happy coding!