I have bound the eval-region function to H-x

I would like to use this to simply highlight selected code and evaluate - simple.

Working in a Python script I have the following code:

def test(this, that):
    output = this * that
    return output

print test(2,4)

When I highlight it and press H-x, I get the error message: "Symbols' value as variable is void: def"

Still having the same code highlighted, in the Python dropdown in the menu bar I click on "eval region" and I get the expected output (i.e. 8).

I have seen an explanation of void variables, but I don't really understand it all - I just want H-x to perform eval-region as clicking on the menu-bar version does.

Does anyone know a fix, work-around or the required setup?

  • 3
    eval-region evaluates only elisp code AFAIK. To see exactly what command is called by the dropdown menu, first hit C-h c or C-h k and then click that menu item. Commented Oct 15, 2015 at 23:29
  • Thanks - it executes (in this case) python-shell-send-region. @kaushalmodi - do you how I could best get the functionality I am looking for?
    – n1k31t4
    Commented Oct 15, 2015 at 23:32

2 Answers 2


What you want is to change what H-x does when in python-mode so that instead of running eval-region (which only works on elisp) it calls python-shell-send-region. You can use define-key to do this:

(with-eval-after-load 'python
  (define-key python-mode-map (kbd "H-x") #'python-shell-send-region))
  • Is having this in my .emacs a bad idea, as it is causing an error which I cannot solve. "Symbol's value as variable is void: python-mode-map". It seems to require a python session to already be in existence - it works if I evaluate at that point. How can I get around this in emacs' initialisation?
    – n1k31t4
    Commented Oct 16, 2015 at 16:16
  • 1
    @DexterMorgan: The problem is that the variable python-mode-map is defined when python-mode is loaded, and your .emacs executes this line before that happened. Please see this answer to a recent question. The comments to this answer address exactly the issue you describe. Commented Oct 16, 2015 at 16:34

The answer from @erikstokes is the correct one (hence why I have accepted it), however in order to get it to work in my init (.emacs) file, I had to define it first as a hook.

(add-hook 'python-mode-hook
          (lambda ()
            (define-key python-mode-map (kbd "H-x")

This allows it to load and then be called upon in python-mode, and doesn't require a python-mode to already be active (hence making in work from my one large init file. [I know it makes sense to break an init file up into sub-files, but I haven't got round to that yet]

  • You simply need to first require the package before calling this add-hook. If you are using use-package, you add that add-hook in the :config block of use-package. Commented Oct 16, 2015 at 17:38
  • Or.. you can put that add-hook in (with-eval-after-load 'PACKAGE-NAME .. ). Commented Oct 16, 2015 at 17:40
  • Is there a big difference/benefit to your suggestion? My way wouldn't require anything at intialisation and so I would expect faster...?
    – n1k31t4
    Commented Oct 16, 2015 at 19:36
  • with-eval-after-load doesn't need any initialization.. it's just one wrapper around the define-key (I realized that I wrote add-hook in my earlier 2 comments instead of define-key; that was a mistake.) .. Adding that define-key to python-mode-hook will unnecessary run that define-key each time you switch to a python-mode buffer or even simply revert that buffer. I find that very inefficient. define-key wrapped with with-eval-after-load will look very much cleaner and will execute just once when the python-mode gets loaded. Commented Oct 16, 2015 at 19:50
  • 1
    I have updated the answer by @erikstokes with with-eval-after-load. Commented Oct 16, 2015 at 19:52

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