Delete space-expanded "tab" in Vim with one keystroke?

I edit Python code with Vim.

With the tab key I get four spaces inserted for indentation. How can I delete those spaces with one "Backspace"(?) stroke - instead of four?

There has to be some "set" option for that...

Here is my .vimrc:

set autoindent
set ts=4
set sw=4
set et

Solution 1:

You can use Ctrl+D to back up one tab stop. This actually moves the whole line to the left one tab stop; Ctrl+T does the same thing to the right. Note that these keystrokes only work in Insert mode (use << and >> for the equivalent in Command mode).

Solution 2:

set softtabstop=4