TL;DR: Use buffers instead of tabs in Vim.
If I understand correctly, the problem is that you want to keep that file in a split window while you change the file on the other side, so that you can keep the other file visible.
It turns out that tabs in Vim don't really work that way, tabs are collections of windows, so whenever you change tabs, you'll switch all windows at once. That's quite useful if you're working on separate sets of windows at the same time.
But it looks like that's not what you want, since you want to change the file in a single window at a time.
For that purpose, you'll want to use buffers in Vim, and not tabs. Buffers are the Vim features that most closely ressembles tabs in other editors such as VS Code.
vim *.py when opening files (without the
-p option that opens them in tabs), and navigate them using
:N). You can then split with
:sp and use the Ctrl-W commands to switch and reorganize windows.
Employ tabs if you ever find yourself wanting to have a separate set of windows, or perhaps focus on a single file full-screen for a while, while at the same time preserving the previous window setup you had, coming back to it at any time.
You might want to read
:help buffers (linked here), it goes into quite a bit of detail into all these concepts.