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Learn how to properly handle YAML files in Python by understanding the steps to parse OpenCV data types using PyYAML.
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This video is based on the question https://stackoverflow.com/q/70732045/ asked by the user 'Young L.' ( https://stackoverflow.com/u/11127401/ ) and on the answer https://stackoverflow.com/a/70732335/ provided by the user 'PApostol' ( https://stackoverflow.com/u/12881844/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Parse YAML File Correctly in Python?

Parsing YAML files can be quite challenging, especially if you are encountering specific data types that are not natively supported by libraries like PyYAML. If you've found yourself stuck with a YAML file—like the one shown below—let’s break down the parsing process step-by-step to ensure everything works smoothly.

Understanding the Problem

You are trying to read a YAML file that includes specific data structures, using the following data format:

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While attempting to parse this file using the PyYAML library, you encountered the following error:

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This error indicates that PyYAML does not know how to handle the opencv-matrix data type in your YAML file. But don't worry—there's a straightforward solution!

Solution Overview

The solution to this parsing problem requires you to define a custom constructor for the OpenCV data type that you are attempting to load. Here’s how you can do it:

Step 1: Import PyYAML

Make sure that you have PyYAML installed in your Python environment. You can install it via pip if you haven't already:

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Step 2: Define the Constructor

Define a constructor function that tells PyYAML how to handle the OpenCV matrix type. Here is the code you would add to your script:

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Step 3: Read the YAML File

Now you can read the YAML file as follows:

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Step 4: Verify the Output

When you run the script, it should successfully parse the YAML file, and you can verify the output:

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The output you receive will look something like this:

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Conclusion

Reading and parsing YAML files that contain specialized data types like OpenCV matrices can be tricky, but by defining a custom constructor in PyYAML, you can successfully interpret the data structure you need. This approach not only resolves the error but enhances your understanding of how PyYAML interacts with various data types.

Now you can confidently work with YAML files in your Python projects! If you encounter any more challenges or have further inquiries, feel free to reach out. Happy coding!