class range
(start, stop[, step])
For a positive step, the contents of a range r
are determined by the formula r[i] = start + step*i
where i >= 0
and r[i] < stop
.
For a negative step, the contents of the range are still determined by the formula r[i] = start + step*i
, but the constraints are i >= 0
and r[i] > stop
.
A range object will be empty if r[0]
does not meet the value constraint. Ranges do support negative indices, but these are interpreted as indexing from the end of the sequence determined by the positive indices.