[Doc Enhancement] More detialed guide to migrate from python to taichi

[STRRL]

Hi taichi folks! Thanks to your amazing work, taichi is a powerful tool that could make fantastic arts.

I participated in the voxel-challenge recently, and I think maybe I found some potential enhancement for taichi's documentation

"taichi" is not "python", you have mentioned that in your documents: https://docs.taichi-lang.org/lang/articles/differences_between_taichi_and_python_programs

Because I used python before, so I write codes in "the python way", and it would not work in taichi without any migration.

For example,

• a simple for-in-slice is not supported with taichi, with a friendly compiler error: "Can only iterate through Taichi fields/snodes (via template) or dense arrays (via types.ndarray)".
• a simple for-in-range is also not supported with tiachi, with "not friendly enough"(I think) error: "list indices must be integers or slices, not Expr". And I finally find the solution, use taichi.staic(range())

So, maybe we could provide an (interactive) tutorial for "how to write codes in taichi way", with some examples and comparisons between python and tiachi. It would be MUCH helpful for beginners to get familiar with and build their confidence to taichi. :)

[neozhaoliang]

This is a very good suggestion. We also have this same idea. Currently the resources on taichi are spread among our examples, doc site and the graphics course on bilibili. Not quite integrated.

Some features like for xxx in xxx is still evolving, for this reason we are hesitate to tell the user "this is the Taichionic way to do it". Anyway I do think such a tutorial would be great for new coming users.