How to Use argparse in Python to Collect Multiple Arguments in a Single List

Learn how to configure Python's `argparse` to gather multiple options into a single list, simplifying your argument handling!
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Mastering Python's argparse to Combine Multiple Options into One List

When working with command-line interfaces in Python, the argparse module is an invaluable tool. It allows developers to easily manage command-line arguments, parse input, and validate options. However, one common issue that many developers encounter is the handling of multiple instances of the same option. This guide will guide you on how to use argparse effectively to ensure that all the specified options are stored in a single list instead of separate lists.

The Problem at Hand

In the example below, you can see an issue with the current implementation of argparse. When the same option is specified multiple times, the parser returns nested lists instead of a flat list:

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

This situation arises when using the action='append' option in argparse, which appends each new occurrence of an argument to a new list. If you desire all inputs to be collected into a single list, read on for the solution!

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

Command Used for Execution

To illustrate the problem, here's the command that was executed:

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

The Desired Result

The desired output format should combine all inputs into a single flat list:

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

The Solution: Using action='extend'

To achieve this outcome, you simply need to change the action parameter in your add_argument method from action='append' to action='extend'. Here's how your code should look after the adjustment:

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

How It Works

action='extend': This option tells argparse to extend the existing list instead of appending a new one. With this setup, whenever the -i argument is specified, the inputs will be added directly to the same list.

Other Parameters: The nargs='+' means that one or more inputs are required for the -i option, while nargs='*' allows for zero or more inputs for the -o option.

Final Thoughts

By simply changing the action to extend, you can efficiently gather all specified inputs into a single list, greatly simplifying the handling of user options in command-line applications. This small adjustment can save time and effort when processing input data in Python.

Now you have the knowledge to enhance your applications with cleaner code and better argument management using argparse. Happy coding!