What are the default slice indices in Python *really*?

Question

From the python documentation docs.python.org/tutorial/introduction.html#strings:

Slice indices have useful defaults; an omitted first index defaults

Answer 1

I don't have any documentation, but I think the default is [None:None:None]

>>> "asdf"[None:None:None]
'asdf'
>>> "asdf"[None:None:-1]
'fdsa'