"""Use the triangle class to represent triangles."""
from math import sqrt
[docs]class Triangle(object):
"""A triangle is a three-sided polygon."""
def __init__(self, a, b, c):
"""Create a triangle with sides of lengths `a`, `b`, and `c`.
Raises `ValueError` if the three length values provided cannot
actually form a triangle.
"""
self.a, self.b, self.c = float(a), float(b), float(c)
if any( s <= 0 for s in (a, b, c) ):
raise ValueError('side lengths must all be positive')
if any( a >= b + c for a, b, c in self._rotations() ):
raise ValueError('one side is too long to make a triangle')
def _rotations(self):
"""Return each of the three ways of rotating our sides."""
return ((self.a, self.b, self.c),
(self.c, self.a, self.b),
(self.b, self.c, self.a))
def __eq__(self, other):
"""Return whether this triangle equals another triangle."""
sides = (self.a, self.b, self.c)
return any( sides == rotation for rotation in other._rotations() )
[docs] def is_similar(self, triangle):
"""Return whether this triangle is similar to another triangle."""
return any( (self.a / a == self.b / b == self.c / c)
for a, b, c in triangle._rotations() )
[docs] def is_equilateral(self):
"""Return whether this triangle is equilateral."""
return self.a == self.b == self.c
[docs] def is_isosceles(self):
"""Return whether this triangle is isoceles."""
return any( a == b for a, b, c, in self._rotations() )
[docs] def perimeter(self):
"""Return the perimeter of this triangle."""
return self.a + self.b + self.c
[docs] def area(self):
"""Return the area of this triangle."""
s = self.perimeter() / 2.0
return sqrt(s * (s - self.a) * (s - self.b) * (s - self.c))
[docs] def scale(self, factor):
"""Return a new triangle, `factor` times the size of this one."""
return Triangle(self.a * factor, self.b * factor, self.c * factor)