The command for repeats part of a program.
It repeats commands that are indented after for.
It's the same as with if - it applies only to
commands that are indented below.
The command for x in range(n): repeats the commands below n times
and it increments the variable x gradually from 0 to n-1.
The command for x in a, b, c, d, ...: repeats the commands below;
it increments the variable x gradually to a, b,
c d, ...