But do you need to? Just write it for bash and run it from fish the same way you run python scripts from bash.

It seems a lot of people don't realize `bash`, `sh`, `zsh` etc... are executable binaries just like any other on the system, and that you don't need to be logged in to a bash shell to run bash scripts.

This isn't the case for sourced scripts. Running a script in bash from fish that changes your current directory will do one of two things: It'll move you to that directory but inside of a bash shell, or it will move you to that directory in a bash shell, bash's cd will return, and you'll be in the same directory as before, still in the fish shell.

The problem is that some scripts are written to be `source`d.

I'm no CLI wizard, so when I sit down to make my own function or alias I'm going to be googling how to do it whether it's for Bash or Fish.

What I meant in my comment above is a lot of 'download an install' instructions in tutorials, and sometimes installation wizards for programs are written for bash, and can't be run without modification in Fish. Not a major setback, but for a Bash user it would just work.