emacs elisp send line if no region active python-mode

I want to create a command where the region is sent if active, and if not, the current line/statement is evaluated and point is taken further to the next statement.

I started with This solution. Now I can't get the (python-shell-send-region) to work though as I don't know how to pass the beginning and end of the region to it.

So far I have this:

 (defun my-python-send-region (&optional beg end)   
   (interactive)   
    (if (use-region-p)
      (python-shell-send-region)    (let ((beg (cond (beg beg)
                    ((region-active-p)
                     (region-beginning))
                    (t (line-beginning-position))))
         (end (cond (end end)
                    ((region-active-p)
                     (copy-marker (region-end)))
                    (t (line-end-position)))))
     (python-shell-send-region beg end)
     (python-nav-forward-statement))))

 (add-hook 'python-mode-hook
       (lambda ()
     (define-key python-mode-map "\C-cn" 'my-python-send-region)))

UPDATE: With Andreas' and Legoscia's suggestions I changed the structure a bit.

Now I get an error (Invalid function: (setq beg (point)) for:

 (defun my-python-send-region (&optional beg end)
  (interactive)
  (if (use-region-p)
    (python-shell-send-region (region-beginning) (region-end))
   ((setq beg (point))
    (python-nav-end-of-statement)
    (setq end (point))
    (python-shell-send-region (beg) (end)))
    (python-nav-forward-statement))))

However, this works:

 (defun my-python-send-region (&optional beg end)
 (interactive)
 (setq beg (point))
 (python-nav-end-of-statement)
 (setq end (point))
 (python-shell-send-region beg end))

Solution

An alternative approach which might work is to try the whole-line-or-region package from melpa. This package sets up things so that if you call a command which expects a region, but no region is defined, it will basically set a region which is equal to the current line. Essentially, this causes commands which expect a region to work when no region is defined on the current line. I have this in my init.org file

Allow region oriented commands to work on the current line if no region is defined.

   #+BEGIN_SRC emacs-lisp
     (use-package whole-line-or-region
       :ensure t
       :diminish whole-line-or-region-mode
       :config
       (whole-line-or-region-mode t)
       (make-variable-buffer-local 'whole-line-or-region-mode))