What is a circular sequence

For our purposes, a circular sequence is a sequence composed by a finite number of elements forming a ring.

Being circular, the first element of the sequence can be considered as also placed just after the last element.

>>> from ring_seq import RingSeq

>>> RingSeq("ABC")[3]
'A'

And the last just before the first.

>>> from ring_seq import RingSeq

>>> RingSeq("ABC")[-1]
'C'

So the "unrolling" of a circular sequence, both forth and backwards, can be assumed as theoretically infinite.

>>> from ring_seq import RingSeq

>>> RingSeq("ABC")[30001]
'B'