line function python

class Line:
    def __init__(self, x1, y1, x2, y2):
        diffx = (x1-x2)
        diffy = (y1-y2)

        c = 0
        if diffx != 0:
            grad = diffy/diffx
            c = y1 - (x1*grad)
        else:
            c = x1
        self.c = c
        self.diffx = diffx
        self.diffy = diffy

    def getY(self, x):
        if self.diffx != 0:
            grad = self.diffy/self.diffx
            return (x*grad) + self.c
        else:
            return None

    def getX(self, y):
        if self.diffx != 0:
            grad = self.diffy/self.diffx
            return (y/grad) - (self.c/grad)
        else:
            return self.c

    def getNormal(self, x, y):
        if self.diffx != 0:
            if self.diffy != 0:
                grad = -1/(self.diffy/self.diffx)
                y2 = y - (grad*x) + (grad*(x+1))
                return Line(x, y, (x+1), y2)
            else:
                return Line(x, y, x, y + 1)
        else:
            return Line(x, y, x + 1, y)

    def getAngle(self):
        if self.diffx != 0 and self.diffy != 0:
            x1, y1 = self.getX(1), 1
            x2, y2 = self.getX(2), 2
            nx = x2 - x1
            ny = y2 - y1
            na = 0
            if nx > 0 and ny > 0:
                na = math.asin(nx/nforce)
            elif nx > 0 and ny < 0:
                na = pi - math.asin(math.fabs(nx)/nforce)
            elif nx < 0 and ny < 0:
                na = pi + math.asin(math.fabs(nx)/nforce)
            elif nx < 0 and ny > 0:
                na = (2*pi) - math.asin(math.fabs(nx)/nforce)
            else:
                raise Exception(" Impossible Coordinates: ", nx, ",", ny)
            return na, False

        elif self.diffx != 0:
            return (0), True
        elif self.diffy != 0:
            return (pi/2), True