class Point:
  def __init__(self, x, y):
    self.x = x
    self.y = y
# Define a class to raise Line errors
class LineError(Exception):  #继承自基类Exception
  def __init__(self,ErrorInfo):
    self.errorinfo=ErrorInfo
  def __str__(self):
    return self.errorinfo
class Line:
  def __init__(self, point1, point2):
    self.point1 = point1
    self.point2 = point2
    if point1.x==point2.x and point1.y==point2.y:
      raise LineError("Cannot create line") 
line = Line(Point(1, 2), Point(1, 2))