For 1-liners there are only 2 real non-shell contenders - Perl and Ruby. Yes you can do them with Python but it ain't pretty.
One-liners are meant to be thrown away, so it does not matter if it's pretty or not. If you care enough to keep it, you should consider rewriting it for clarity. That last step does not require using any particular language; e.g. my PS1 started off as an increasingly convoluted one-liner, until I rewrote it in Go.
PS1 in Go? Overkill, doesn't come close.
Depends on what you're trying to do. If you're shelling out to git(1) or docker(1), rather than e.g. recursively checking for the presence of .git in parent directories, or inspecting ~/.docker/config.json, then the fork+exec overhead is already quite significant. Next if you're parsing ~/.docker/config.json in shell, you're most likely either asking for trouble or (again) shelling out to jq. Writing it all in an interpreted language means you're paying the cost of interpreter startup, which on underpowered systems can take hundreds of milliseconds even when idle. OTOH loading a static binary to memory happens only once, and with Go you can trivially cross-compile.
I also have a fallback shell one-liner, without any of the fanciness like displaying the current git branch:
https://github.com/rollcat/etc/tree/master/cmd/prompter#i-li...
Once you need to do fancy array manipulation, hash tables, data structures, etc you're very likely much better off with Python, Perl, Ruby, Lua, Tcl, JS, or literally anything else. Notably, one or both of Python and Perl are available out of the box on Debian (and derivatives), macOS, most (all?) BSDs, and so on. Targeting Python 3.6+ will probably cover 99%+ of the systems you can find in the wild (e.g. Ubuntu 18.04 and newer).
I have also had some minor success using Go for that purpose. The toolchain can trivially cross-compile executables for ca 40 different OS/arch combinations; you need to consider the os/arch if you're running something different than Linux/x86-64 but that will again likely put you in the 1%. I'm working on some tooling to make this approach more straightforward.