Скачать или смотреть How to Successfully Print an Object from a Class in Python

Learn how to effectively display object attributes in Python by using the `__str__` and `__repr__` methods for clear and readable output.
---
This video is based on the question https://stackoverflow.com/q/72763605/ asked by the user 'Elix' ( https://stackoverflow.com/u/19421032/ ) and on the answer https://stackoverflow.com/a/72763636/ provided by the user 'A l w a y s S u n n y' ( https://stackoverflow.com/u/1138192/ ) 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: Can't print an object from a class

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.
---
Understanding Object Printing in Python

As a beginner in Python, you might face challenges when trying to print objects defined in classes. This is a common hurdle that many face during their journey in programming, particularly in object-oriented programming (OOP).

In this guide, we will address a specific issue about printing an object from a class and provide a detailed solution. If you’ve encountered an output like <__main__.Person object at 0x000002C5DFB02050> when trying to print an object's attribute, you are not alone!

Let’s dive into understanding how to resolve this issue effectively.

The Problem

Consider the following code snippet:

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

In this setup, when you execute print(dog.owner), instead of getting the owner's name, you receive:

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

This output isn't user-friendly and doesn't display the name of the Person. The reason for this is that the Person class does not have a method defined to return a string representation of its instance.

The Solution

To resolve this issue, you can implement two special methods in your classes: _str_ and __repr__. These are known as "dunder" methods (short for double underscores) that allow you to define how an object should be represented as a string.

Step 1: Implementing _str_ and _repr_

You can define these methods in both the Dog and Person classes as follows:

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

Step 2: Understanding the Output

_str_ Method: This method is called when we use print() on an object. It is meant to provide a "nice" or user-friendly string representation.

_repr_ Method: This method is intended for a more developer-friendly representation and is useful for debugging. It can be invoked with the repr() function or in the interactive shell.

By implementing these methods, you will now get a more readable output. For example:

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

Important Notes

If you attempt to print an object without defining these methods, Python will default to printing the memory address of the object, which is not helpful.

You can customize these methods further depending on the attributes you want to display.

Conclusion

In conclusion, printing an object from a class in Python requires defining the _str_ and/or _repr_ methods to create usable and engaging string representations of your objects. Don't hesitate to format these outputs to make your debug or user interface friendlier and more informative.

By following the steps outlined in this guide, you should be able to modify your classes to successfully print their attributes in a clear manner.