Vision application to detect object angle WRT vertical and horizontal.

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Python

OpenCV

I want to develop a vision application to detect the angle of an object with respect to horizontal and vertical.
I need someone's assistance to understand the basics of object detection, and what all functions and Libraries are required for this project.

What I have tried:

I have very little basics of Vision application. I have developed some applications with OpenCV for OCR applications. I tried object detection using OpenCV Countours, and need support for Implementing Learning Model for correct Object Detection.