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](http://www.gnu.org/software/emacs/manual/html_node/elisp/Void-Variables.html) 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?