How to explain the reverse of a sequence by slice notation a[::-1]

Question

From the python.org tutorial

Slice indices have useful defaults; an omitted first index defaults to zero, an omitted second index defaults to the size

Answer 1

You are confused with the behavior of the stepping. To get the same result, what you can do is:

a[0:5][::-1]
'olleh'

Indeed, stepping wants to 'circle' around backwards in your case, but you are limiting it's movement by calling a[0:5:-1].