UltiSnips

UltiSnips is the ultimate solution for snippets in Vim. It has many features, speed being one of them. You should first expand the #! snippet, then the class snippet. The completion menu comes from YouCompleteMe, UltiSnips also integrates with deoplete, and more. You can jump through placeholders and add text while the snippet inserts text in other places automatically: when you add Animal as a base class, __init__ gets updated to call the base class constructor. When you add arguments to the constructor, they automatically get assigned to instance variables. You can then insert your personal snippet for print debugging.