Is it possible without any plugins?
Or what's the best plugin for edit python file?
I normally use vip or any of the above depending on the need, do not forget that you can always select up (i.e., down =)) to the next occurrence using v/match (followed by Enter to confirm, and possibly n for next). For python, you could look for the next def or for the return (ret is normally enough).  
This isn't the fastest at the beginning, but it is very general, use it in any language and also outside coding (md, latex, etc.).
what's the fastest way to select a function of Python via VIM?