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

# Triangle Project Code.


# triangle(a, b, c) 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):
    # Checks if any of the sides is less than 0
    if a <= 0 or b <= 0 or c <=0: raise TriangleError
    
    # Pitagoras.
    x,y,z = sorted([a,b,c]);
    if x + y <= z: raise TriangleError
    
    if a == b == c:
        return 'equilateral'
    elif (a == b) or (a == c) or (b == c):
        return 'isosceles'
    else:
        return 'scalene'
    
# Error class used in part 2.  No need to change this code.
class TriangleError(StandardError):
    pass