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Implementing Ordered and Repeated Flags Using argparse in Python

Discover how to leverage Python's `argparse` library to create a command-line interface that handles ordered and repeated flags efficiently. --- This video is based on the question https://stackoverflow.com/q/63581675/ asked by the user 'Andy Lambert' ( https://stackoverflow.com/u/14164507/ ) and on the answer https://stackoverflow.com/a/63586345/ provided by the user 'hpaulj' ( https://stackoverflow.com/u/901925/ ) 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: Ordered and repeated flags 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. --- Implementing Ordered and Repeated Flags Using argparse in Python When developing command-line interfaces (CLIs) in Python, users often encounter the need to invoke specific methods in a desired order. For instance, invoking methods like this: [[See Video to Reveal this Text or Code Snippet]] This challenge leads developers to ask whether it's possible to capture such flags in a structured order without having to entirely write a parser from scratch. Fortunately, using Python's built-in argparse library, we can efficiently handle ordered and repeated flags. In this post, we'll walk through how to set up an argparse parser that allows repeated flags in the specified order. The Challenge When you use a typical argument parser, executing commands can result in losing the order of execution or requiring additional handling to process the flags correctly. The goal here is to utilize argparse features to gather commands in a list while maintaining their order. Example of the desired output Running the command: [[See Video to Reveal this Text or Code Snippet]] Should yield a structured output that reflects the repeated, ordered nature of the commands: [[See Video to Reveal this Text or Code Snippet]] Solution: Setting Up the Argument Parser We can accomplish this by using the argparse library’s append_const. Let’s break down the steps. Step-by-Step Implementation Import argparse: Start by importing the argparse module. [[See Video to Reveal this Text or Code Snippet]] Create the Argument Parser: Initialize an ArgumentParser instance. [[See Video to Reveal this Text or Code Snippet]] Add the Command-line Arguments: Use the add_argument method to define your flags. The action='append_const' parameter allows us to collect the flags repeatedly. [[See Video to Reveal this Text or Code Snippet]] Parse the Arguments: Use the parse_args method to process the input, which captures input from the command line. [[See Video to Reveal this Text or Code Snippet]] Iterate Through Commands: Finally, you can loop through the list of commands and execute them as needed. [[See Video to Reveal this Text or Code Snippet]] Example Function Hooks To make this even more functional, you can hook actual functions to be executed for each command. Let’s say we define a function for doA: [[See Video to Reveal this Text or Code Snippet]] You could modify the setup slightly: Change const='doA' and const='doB' to const=doA and const=doB, and Reorganize the execution to call these functions. [[See Video to Reveal this Text or Code Snippet]] Conclusion With argparse, handling ordered and repeated flags is straightforward and keeps your command-line interface clear and user-friendly. This structured approach allows you to extend your command-line tool with various functionalities while keeping the parsing simple and efficient. For more complex scenarios involving multiple arguments, consider using parser.add_argument with nargs and choices for added flexibility. Engaging with the capabilities of Python’s argparse lets you create robust, user-friendly command-line applications. We hope this guide has provided you with a clear path to implement your own ordered and repeated flags. Happy coding!