How to comment out a block of Python code in Vim

Step 1: Go to the the first column of the first line you want to comment.

Step 2: Press: Ctrl+v and select the lines you want to comment:

Step 3: Shift-I#space (Enter Insert-at-left mode, type chars to insert. The selection will disappear, but all lines within it will be modified after Step 4.)

Step 4: Esc

one way manually

:set number
:10,12s/^/#

You could add the following mapping to your .vimrc

vnoremap <silent> # :s/^/#/<cr>:noh<cr>
vnoremap <silent> -# :s/^#//<cr>:noh<cr>

Highlight your block with:

Shift+v

# to comment your lines from the first column.

-# to uncomment the same way.