There are some old tickets about changing splitext() in 2007:
https://bugs.python.org/issue1115886
https://bugs.python.org/issue1681842

Present python documentation:
Leading periods on the basename are ignored; splitext('.cshrc') returns ('.cshrc', '').
Changed in version 2.6: Earlier versions could produce an empty root when the only period was the first character.

But nobody take care about more than one dots:
For example this possible corect filenames:

>>> os.path.splitext('....jpg')
('....jpg', '')

So present function is insuficient (buggy) to use to detect right extension.
Maybe new parameter would be helpfull for that?
Like parameter "preserve_dotfiles" discussed in 2007.

And what to do with the wrong '.', '..', '...', ... filenames?