Question

I’m trying to open a file on Ctrl-f. If the command is
typed in the presence of an empty buffer ‘None’ then I
want the file to be opened in that buffer, but if there
is no empty buffer I’d like to open a new buffer using
:tabnew and then open the file in that.
For this purpose I have a function OpenFile which is
invoked.

function! OpenFile()
python << EOF
import vim
import re
buffer = vim.current.buffer
name = str(buffer.name)
if re.match('None', name):
    vim.command(':e ')
else:
    vim.command(':tabnew')
    vim.command(':e ')
EOF
endfunction

"Open file
 :map <C-f> :call OpenFile()<CR> 
:imap <C-f> <Esc>:call OpenFile()<CR>

vim.command executes the command so this is equivalent to
:w!ENTER What I want to do is setup part of the command..
:e FILENAME ENTER

So I want to send the :e part in Ex mode via the
python-function and get the user to type the filename
and hit ENTER

Answer 1

First of all, why do you write this in Python? Sure, Vimscript is a bit strange (but since Vim 7 is has become a lot like Python), and you need to learn about the integration points, anyway, and this task has very little real logic in it.

This is easiest solved via a map-expression (:help map-expression):

:noremap <expr> <C-f> empty(bufname('')) ? ':edit ' : ':tabnew '

If you must, extract the conditional into a function and code it in Python, but I would recommend sticking to Vimscript, unless the logic is really complex or you could benefit from certain libraries.