Autocmds for particular filetypes

Question

I'm trying to understand using the autocmd to modify properties for certain files. Here is a basic example I have in my vimrc:

syntax on
autocmd BufRead *.py syntax off

However, when I then open up a new python file, all files in that window (whether python or not) have their syntax highlighting removed. For example:

Why does this occur, and what would be the proper way to change something for only the filetype I'm referencing and not other windows/splits?

Note: the same thing also happens with:

autocmd FileType python syntax off

From Learn Vimscript the Hard Way:

One of the most useful events is the FileType event. This event is fired whenever Vim sets a buffer's filetype.

But if the user has to manually set the ft everytime a file is opened, it seems quite useless (if I'm understanding things correctly).

Answer 1

The :syntax command is global. Probably you're looking for the "local to buffer" setting 'syntax' (abbreviation: 'syn'). To disable for current file:

set syn=OFF

per :h 'syn' though set syn= and set syn& seem to work, too.

You can use this with a filetype auto command like so:

autocmd FileType python set syn=OFF

Each time you open a Python file it should be without syntax highlighting.

(I wouldn't be surprised if there were other ways to accomplish this but I verified the above works.)