URL encode/decode vim selection.

.vimrc

" URL encode/decode selection
vnoremap <leader>en :!python -c 'import sys,urllib;print urllib.quote(sys.stdin.read().strip())'<cr>
vnoremap <leader>de :!python -c 'import sys,urllib;print urllib.unquote(sys.stdin.read().strip())'<cr>

Clever trick 👌
If someone ends up here looking for a native Vimscript solution

function! UrlEncode(mystring)
let urlsafe = ""
for char in split(join(lines, "\n"), '.\zs')
    if matchend(char, '[-_.~a-zA-Z0-9]') >= 0
        let urlsafe = urlsafe . char
    else
        let decimal = char2nr(char)
        let urlsafe = urlsafe . "%" . printf("%02x", decimal)
    endif
endfor
echo urlsafe
" return urlsafe
endfunction

I ran into some issues with running the leader commands above with Python 3. These work though:

" URL encode/decode selection
vnoremap <leader>en :!python3 -c 'import sys; from urllib import parse; print(parse.quote_plus(sys.stdin.read().strip()))'<cr>
vnoremap <leader>de :!python3 -c 'import sys; from urllib import parse; print(parse.unquote_plus(sys.stdin.read().strip()))'<cr>

if you have nodejs installed

:'<,'>!node -e 'console.log(decodeURIComponent(process.argv[1])))' -- `cat`