How to Deep-Copy a Class Object in Python3

Learn the steps to deep-copy a class object in Python3, ensuring full isolation from the original class and its attributes.
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How to Deep-Copy a Class Object in Python3

When working with classes in Python, there are scenarios where you may want to create an entirely independent copy of a class object. This brings us to a common question: How can you deep-copy a class object in Python3?

In this guide, we will explore the issues that arise when trying to copy class objects using standard methods and provide creative solutions to achieve the desired result.

The Problem

Consider the following class structure and the goal you wish to achieve:

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Your objective is for this code to output:

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However, using standard copy methods like copy.deepcopy() leads to unintended shared attributes between the original and the copied class. That is, changes made to one will affect the other.

Analyzing the Standard Copy Method

The copy.deepcopy() function seems straightforward but does not fulfill our need for a complete separation. For instance:

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This setup leads to the unexpected conclusion that both the original class and the copied class share the same properties, which is not what we intended.

Alternative Solutions

Given that the standard methods fall short, let’s explore some alternatives.

1. Using Inheritance

One effective way to isolate class objects is by utilizing inheritance. Here’s how to implement this:

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This will give you the output:

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By this method, changing attributes in class B does not affect A. However, note that isinstance(b, A) returns True, which may not always be desirable.

2. Creating Dummy Classes

To avoid the inheritance issues and ensure proper isolation, we can create a dummy base class. Here’s how:

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Now, when you check:

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Conclusion

In conclusion, to deep-copy a class object in Python3 so that it is entirely isolated from its original, employing inheritance and dummy classes serves as an effective approach. This method ensures that changes made to one class do not affect the other, fulfilling your requirements elegantly.

Feel free to try out the code snippets provided and adapt them for your projects. Happy coding!