1+2+3+....+100

@Sphinx My inclination would be to write that as:

n = 100
counter = 1
while counter <= n:
counter += 1

I think that "sum" is unnecessary. You could add "step" variable, if you don't want to count by ones.

@Lwasserman wha? the sum is the whole point of the exercise, always read the problem carefully, kids...

@Sphinx