Write a Python Program: Defines two classes, Point() and Triangle(). An object f

Question

Write a Python Program:

Defines two classes, Point() and Triangle().

An object for the second class is created by passing named arguments, point_1, point_2 and point_3, to its constructor.

Such an object can be modified by changing one point, two or three points thanks to the method change_point_or_points().

At any stage, the object maintains correct values for perimeter and area.

Below is a half cooked solution which needs to be completed

# Defines two classes, Point() and Triangle().
# An object for the second class is created by passing named arguments,
# point_1, point_2 and point_3, to its constructor.
# Such an object can be modified by changing one point, two or three points
# thanks to the method change_point_or_points().
# At any stage, the object maintains correct values
# for perimeter and area.

from math import sqrt

class PointError(Exception):
def __init__(self, message):
self.message = message

class Point():
def __init__(self, x = None, y = None):
if x is None and y is None:
self.x = 0
self.y = 0
elif x is None or y is None:
raise PointError('Need two coordinates, point not created.')
else:
self.x = x
self.y = y
  
def collinear(self, p2, p3):
if (p2.y - self.y) * (p3.x - p2.x) ==
(p3.y - p2.y) * (p2.x - self.x):
return True
return False

class TriangleError(Exception):
def __init__(self, message):
self.message = message

class Triangle:
def __init__(self, *, point_1, point_2, point_3):
if point_1.collinear(point_2, point_3):
self.error_message('Initialisation')
else:
self._initialise(point_1, point_2, point_3)

def change_point_or_points(self, *, point_1 = None,point_2 = None, point_3 = None):
if not self._change_point_or_points(point_1, point_2, point_3):
print('Could not perform this change.')
return

def _initialise(self, p1, p2, p3):
self.p1 = p1
self.p2 = p2
self.p3 = p3
length_12 = self._side_length(p1, p2)
length_13 = self._side_length(p1, p3)
length_23 = self._side_length(p2, p3)
self.perimeter = length_12 + length_13 + length_23
half_perimeter = self.perimeter / 2
self.area = sqrt(half_perimeter *
(half_perimeter - length_12) *
(half_perimeter - length_13) *
(half_perimeter - length_23))

def _change_point_or_points(self, p1, p2, p3):
if not p1:
p1 = self.p1
if not p2:
p2 = self.p2
if not p3:
p3 = self.p3
if p1.collinear(p2, p3):
self.error_message('Update')
return False
else:
self._initialise(p1, p2, p3)
return True

def _side_length(self, p, q):
return sqrt((q.x - p.x) ** 2 + (q.y - p.y) ** 2)

# Possibly define other methods
  

Explanation / Answer

Not much change was required.

from math import sqrt

class PointError(Exception):
def __init__(self, message):
self.message = message

class Point():
def __init__(self, x = None, y = None):
if x is None and y is None:
self.x = 0
self.y = 0
elif x is None or y is None:
raise PointError('Need two coordinates, point not created.')
else:
self.x = x
self.y = y
  
def collinear(self, p2, p3):
if (p2.y - self.y) * (p3.x - p2.x) ==
(p3.y - p2.y) * (p2.x - self.x):
return True
return False

class TriangleError(Exception):
def __init__(self, message):
self.message = message

class Triangle:
def __init__(self, point_1, point_2, point_3):
if point_1.collinear(point_2, point_3):
self.error_message('Initialisation')
else:
self._initialise(point_1, point_2, point_3)

def change_point_or_points(self, point_1 = None,point_2 = None, point_3 = None):
if not self._change_point_or_points(point_1, point_2, point_3):
print('Could not perform this change.')
return

def _initialise(self, p1, p2, p3):
self.p1 = p1
self.p2 = p2
self.p3 = p3
self.perimeter,self.area = self.peri_area(self.p1,self.p2,self.p3)
print(self.p1.x,self.p1.y,self.p2,self.p3,self.perimeter,self.area)

def peri_area(self, p1,p2,p3):
length_12 = self._side_length(p1, p2)
length_13 = self._side_length(p1, p3)
length_23 = self._side_length(p2, p3)
perimeter = length_12 + length_13 + length_23
half_perimeter = perimeter / 2
area = sqrt(half_perimeter *
(half_perimeter - length_12) *
(half_perimeter - length_13) *
(half_perimeter - length_23))
  
#print(self.p1.x,self.p1.y,self.p2,self.p3,self.perimeter,self.area)
return(perimeter,area)

def _change_point_or_points(self, p1, p2, p3):
if not p1:
p1 = self.p1
if not p2:
p2 = self.p2
if not p3:
p3 = self.p3
if p1.collinear(p2, p3):
self.error_message('Update')
return False
else:
self._initialise(p1, p2, p3)
return True

def _side_length(self, p, q):
return sqrt((q.x - p.x) ** 2 + (q.y - p.y) ** 2)

p1 = Point(0,0)
p2 = Point(2,0)
p3 = Point(2,1)
tri = Triangle(p1,p2,p3)
p4 = Point(2,2)
tri.change_point_or_points(p1,p2,p4)
# Possibly define other methods

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