How to keep underscores in Python within a word boundary?

Question

When writing code in python-mode my preference would be to include underscores within a word boundary, so variable_with_underscores is treated as a single word.

How would I limit my word preference only to python-mode?

Answer 1

Add a hook to modify the python-mode-syntax-table:

;; Keep underscores within a word boundary
(add-hook 'python-mode-hook
          (lambda () (modify-syntax-entry ?_ "w" python-mode-syntax-table)))

Answer 2

It's bird, it's a plane, it's superword-mode:

Superword mode is a buffer-local minor mode. Enabling it changes the definition of words such that symbols characters are treated as parts of words: e.g., in ‘superword-mode’, "this_is_a_symbol" counts as one word.

It's a minor mode, so you can set it in a hook the normal way: (add-hook 'python-mode-hook #'superword-mode). superword-mode has only existed since 24.4, so you'll need to hack the syntax table by hand in older versions.

I find it very convenient to bind this to a key so I can easily toggle it. It's the sort thing I want sometimes, but not others.