New REPL: `python -q` outputs unnecessary blank space on empty terminal

Bug report

Bug description:

If I start the new REPL on a clear terminal, I get an unnecessary blank space.

clear; python -q

Whereas this does not happen if I run the old ("basic") REPL:

clear; PYTHON_BASIC_REPL=1 python -q

Analysis

I've tracked this down to these 2 lines of code: https://github.com/python/cpython/blob/3.13/Lib/_pyrepl/unix_console.py#L241-L242

self.__move(0, len(self.screen) - 1)
self.__write("\n")

I don't totally understand this code, but it certainly smells like there's a bug here when dealing with an empty screen (for example, if len(self.screen) == 0, are we trying to move the cursor to index -1?)

I'm not sure what the fix is here, though. I don't really understand this code: why are we moving up to a line just to move the cursor down a line afterwards? why can't we jump straight to where we want to be? I tried digging through the git history for answers, but it looks like this incantation dates back all the way to this initial commit to pypi/pyrepl. I'm not sure how to dig any further back in time.

CPython versions tested on:

3.13, 3.14, CPython main branch

Operating systems tested on:

Linux

I'm using Alacritty, in case that's relevant.

Linked PRs

• gh-131907

Start by reproducing the blank space with clear; python -q and compare it with PYTHON_BASIC_REPL=1 python -q. Read Lib/_pyrepl/unix_console.py around lines 241-242, including the __move and __write calls, and review linked PR gh-131907. Done means the new REPL no longer emits the unnecessary blank space on an empty terminal.