How to Update a Variable Value in a Child Class Using Kwargs in Python

A step-by-step guide on dynamically updating class variables in Python using keyword arguments (kwargs) in an inherited class structure.
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This video is based on the question https://stackoverflow.com/q/68995394/ asked by the user 'Muhammad Daniyal' ( https://stackoverflow.com/u/14070224/ ) and on the answer https://stackoverflow.com/a/68995622/ provided by the user 'Alexandre Mahdhaoui' ( https://stackoverflow.com/u/15515206/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Update a Variable Value in a Child Class Using Kwargs in Python

When working with Python classes, especially in an inheritance hierarchy, it is common to initialize variables in a parent class and need to update these in a child class. If you've faced a situation where you want to pass in dynamic values through keyword arguments (kwargs) to modify these variables, you're not alone. This post will walk you through an effective way to update variable values in a child class using kwargs.

Problem Overview

Consider the following scenario: You have two classes, where one is a parent and the other a child. The parent class holds some variables, and you want the child class to potentially update these variables based on input when an instance of the child is created.

The Initial Setup

You start with a parent class that initializes two variables:

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

Next, in your child class, you want to accept these kwargs:

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

When creating an instance of XYZ, you'd like to do something like this:

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

The Solution: Updating Class Variables with Kwargs

Step 1: Initialize the Parent Class

To start, you should initialize the parent class within the child class using super(). This sets up the variables defined in the parent.

Step 2: Accessing Instance Variables

Once the parent class is initialized, you can access the instance variables through self.__dict__, which contains the current state of the instance's attributes.

Step 3: Iterating Over the Keyword Arguments

You then want to loop through the kwargs and check if the keys match the current instance variables. If they do, you can update their values.

Here is how you can implement these steps in your child class:

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

Putting It All Together

With the above implementation, when you create an instance of XYZ like so:

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

This will successfully update var_1 to 'updated_value'.

Key Takeaways

Using **kwargs in class constructors allows you to pass dynamic values.

Always initialize the parent class first with super().

Use self.__dict__ to safely access the instance's attributes and ensure the keys match the defined variables.

By following these steps, you can effectively manage and update variable values in a child class based on the input provided during initialization. This technique not only makes your classes more versatile but also prevents the introduction of unexpected variables, safeguarding your class structure.

Now you can confidently apply this method in your Python projects!