Programmers of other programming languages like C or C++ are used to a different kind of for loops:
for (i = 0; i < n; i++) printf("%d, ",i);
Such a behaviour can be imitated in Python with the help of the range() function:
>>> range(5)
[0, 1, 2, 3, 4]
>>> range(3,7)
[3, 4, 5, 6]
>>> range(3,20,4)
[3, 7, 11, 15, 19]