Can't use variables in pygame.draw.circle?

barrely = barrely + 0.1

barrely must be a float at some point because of this line.

I think you should do pygame.draw.circle(screen, (0,255,0), (int(barrelx), int(barrely)), 64, 0) to truncate the variables to integers as the function requires.

You don't say which line is giving the error, but if you're using Python 3, / gives a float result. Use // for an integer.