PEP8 use `_` as a word delimitor, for example, a method named `get_context_data`.

`caw` is so cool when you want change `get_context_data` to `set_context_data`.

I googled and added `set iskeyword-=_` to my vimrc.

But another problem comes with this change, I can autocomplete the method name when I type `get_`, menu shows me `context` not `context_data` I want, is there a way to solve the problem?