Vectorize inefficient python for loops with numpy

[maldil]

Hi Maintainers of this repo,

Thank you very much for your excellent work, I am new to this repository. I am a researcher studying the best practices of evolving data science codes. According to our findings after examining 1000 data science repositories, migration of loop-based calculations is a widespread evolution practice among developers since it improves performance and code quality. I created this PR to make better use of NumPy functions and avoid unnecessary loops.

This PR is a minor contribution compared to all the hard work that you have done in this repo. However, I am hoping that it will enhance code quality and, hopefully, performance.

[maldil]

@stephantul could you please help to merge this PR

[Thynix]

@maldil You say hopefully it'll improve performance - it sounds like you didn't test it?