Question

I am selecting some text via Ctrl-v (visual mode). Then I type
\s to align those lines and sort them like so:

"Strip trailing space
 :map <Leader>S :1,$ s/\s\+$//g<CR>
:imap <Leader>S :1,$ s/\s\+$//g<CR>

How do I pass all the selected lines to Sort(). I thought the
vim.current.range object might do it but that didn’t work out.
Currently the Sort() function reads text 1 line at a time via
cr[0]. What I need to do is store the split lines in a matrix,
compute the required length/column and print them out into the
buffer.

function! Sort()
python << EOF
import vim
cr = vim.current.range
line = cr[0]
line = line.split()
fmt_str = ['%8s' for word in line]
fmt_str = ' '.join(fmt_str)

line = tuple([word for word in line])
print(fmt_str)
cr[0]= fmt_str % line
EOF
endfunction

"Sort and align
:map <Leader>s :call Sort()<CR>

Answer 1

When you want a mapping to work on the visual selection, you need to use :vnoremap. An Ex command (like :call) will then automatically have the visual range '<,'> prepended. An ordinary function would then be invoked once per line, but you can define a special kind of function (cp. :help function-range-example) that handles the range itself.

Since you seem to want to use Python, I’d just drop the prepended range via <C-u> and access the selection’s bounds via the < and > marks, then access and modify the lines via vim.current.buffer[lnum]:

:vnoremap <Leader>s :<C-u>call Sort()<CR>
function! Sort()
    ...
    start = vim.current.buffer.mark('<')[0]
    end = vim.current.buffer.mark('>')[0]