Python line-drawin algo

    def drawLine(self, x1, y1, x2, y2, aamode = 0):
        ''' Draws a line between the points *(x1, y1)* and *(x2, y2)* in the
            current pen-color. *aamode* defines the use of anti-aliasing.

            .. note:: Anti-aliasing is not implemented yet. '''
        if x2 < x1:
            x1, x2 = x2, x1

        # 1. we need to calculate the slope of the line, remember the good old
        #    linear-function formula from maths: f(x) = mx + t
        slope = (y2 - y1) / (x2 - x1)

        # 2. we will now iterate over the full length of the line in x-direction
        #    and calculate the corresponding y-value
        for x in xrange(x2 - x1):
            y = slope * x + y1
            x = x + x1
            self.setPixel(x, y)