Keep in mind that you're able to repeat the last used command with @:
, so that's all you'd need to repeat are those two character.
Or you could save the string w !python
into one of the registers (like "a
for example) and then hit :<C-R>a<CR>
to insert the contents of register a
into the commandline and run it.
Or you can do what I do and map <leader>z
to :!python %<CR>
to run the current file.