How to Use an ArgumentParser Argument as a Default Value for Another Argument in Python

Discover how to set an `ArgumentParser` argument as a default value for another argument effectively, enhancing your Python scripts with dynamic default options.
---

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: Use an ArgumentParser argument as a default value of another argument

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Use an ArgumentParser Argument as a Default Value for Another Argument in Python

In the world of Python programming, especially when working with command-line interfaces, argument parsing is an essential skill. One frequent challenge developers encounter is setting one argument as the default value for another within an ArgumentParser. This can be particularly useful for creating dynamic scripts that adapt based on user input. If you're wondering how to achieve this, you've come to the right place!

Understanding the Problem

Imagine you have a script that requires inputted paths for certain files. You want to allow users to specify a primary file path, and if they don't provide a secondary option, it should default to the primary file path. In your initial attempt, you might try to directly reference the primary path as the default for the second argument, but this won't work as intended because the parser doesn't have the argument values yet.

Example of the Desired Behavior

Here's a quick outline of what you're looking to achieve:

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

The Solution: Using parse_known_args()

Step-by-Step Guide

To set an argument's default value based on another argument in the same parser, follow these steps:

Define Your Arguments: First, create the ArgumentParser and define your initial arguments.

Parse Known Arguments: Use parse_known_args() initially to parse options you know you want, such as the primary path.

Set the Default for the Second Argument: After obtaining the value of the first argument, you can use that value as the default for the second argument.

Parse Again: Finally, parse the arguments again to ensure you have all the provided values.

Implementation

Here's how you can implement this in your Python script:

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

Conclusion

Using ArgumentParser in Python can greatly enhance your script's usability, especially when dealing with command-line inputs. By following the above method, you can elegantly set up default values based on other inputs without hassle. This functionality not only improves user experience but also helps create cleaner and more adaptable code.

Now that you have the tools and knowledge to set one ArgumentParser argument as the default for another, you can start enhancing your scripts right away! Happy coding!