Options such as expandtab reset based on which file I edit

Question

My ~/.vimrc contains the following:

set noet
set ts=8
set sw=8

When I open vim without arguments:

:set et? -> noexpandtab

and

:set sw? -> shiftwidth=8

but when I open a file: :e somefile.py

:set et? -> expandtab

and

:set sw? -> shiftwidth=4

but editing ~/.vimrc yields the same results like when I opened vim without arguments

Why does this happen and how to fix it?

Answer 1

Vim may override your global settings with filetype-specific settings through filetype plugins. (There are also indent plugins that can affect this behavior.)

In the specific case of Python shift width and tab expansion, this behavior is enabled by script $VIMRUNTIME/ftplugin/python.vim which ships with Vim.

Note that, in the specific case of the Python options you mentioned, you can override them by setting a global variable to tell Vim you'd like it not to set them. You can do so by adding this variable setting to your vimrc:

let g:python_recommended_style = 0

This behavior (and the variable to override it) is documented under :help ft-python-plugin.