Range

Question

Why the number 10 wasn't appearing?
numbers.range(10)
print(numbers)

output will be 0 - 9
is it just count 0 as one?

Answer 1

Just in math it is useful to cancatenating half-ranges. Half-ranges mean that lower number in notation IS IN range, but larger IS NOT.
range(10) ==> [0; 10) // including 0, excluding 10

Union for half-ranges that have end on the same number has next property: each number in result repeats once. But so can't be archived in usual ranges. Compare:

[0; 5) U [5; 10) = [0; 10)
(0,1,2,3,4) U (5,6,7,8,9) = (0,1,2,3,4,5,6,7,8,9)

And

[0; 5] U [5; 10] = [0; 10] but '5' appears twice

Answer 2

Also, length of half-range is easy to count. Just find difference between begin and end of half-range

Answer 3

range(10) means one number less i mean range(5) will print 0 to 4
etc.