#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Triangle Project Code.

# Triangle analyzes the lengths of the sides of a triangle
# (represented by a, b and c) and returns the type of triangle.
#
# It returns:
#   'equilateral'  if all sides are equal
#   'isosceles'    if exactly 2 sides are equal
#   'scalene'      if no sides are equal
#
# The tests for this method can be found in
#   about_triangle_project.py
# and
#   about_triangle_project_2.py
#
def triangle(a, b, c):
    sides = [a, b, c]

    # any negative sides
    if len(list(filter(lambda x: x < 0, sides))) > 0:
        raise TriangleError
    # the triangle equality
    if not all([a + b > c, a + c > b, b + c > a]):
        raise TriangleError

    sides_count = len(set(sides))
    if sides_count == 3:
        return 'scalene'
    elif sides_count == 2:
        return 'isosceles'
    else:
        return 'equilateral'

# Error class used in part 2.  No need to change this code.
class TriangleError(Exception):
    pass
