Shape class

gistfile1.py

class Shape(object):
    __delimiter = "_"

    def __init__(self):
        """
        >>> shape = Shape()
        >>> shape.add([1, 2, 3, 4])
        >>> shape.add([1, 2, 5, 6])
        >>> shape.add([3, 4, 7, 8])
        >>> shape.outlines()
        [[1, 4], [1, 6], [2, 3], [2, 5], [3, 8], [4, 7], [5, 6], [7, 8]]
        """
        self.lines = {}

    def add(self, ids):
        for line_hash in self.__line_hashes(ids):
            self.lines[line_hash] = self.lines.get(line_hash, 0) + 1

    def outlines(self):
        return sorted([int(x) for x in k.split(Shape.__delimiter)] for k, v in self.lines.items() if v == 1 )

    @staticmethod
    def __line_hashes(ids):
        """
        >>> Shape._Shape__line_hashes([1, 2, 3, 4])
        ['1_2', '2_3', '3_4', '1_4']
        """
        ids.append(ids[0])
        return [Shape.__delimiter.join(sorted([str(ids[i]), str(ids[i+1])])) for i in range(len(ids)-1)]


if __name__ == "__main__":
    import doctest
    doctest.testmod()