ex5_1.py

"""
Write a class representing two-dimensional vector (with x and y coordinates),
which supports the following operations:
1. Addition of two vectors: v1 + v2
2. Subtraction of two vectors: v1 - v2
3. Dot product of two vectors:
    a. Using operator v1 * v2
    b. Using method v1.dot(v2)
    c. Using class method Vector2d.dot(v1, v2)
4. Vector length property:
    a. v.length
5. String representation: str(v)
"""

from math import sqrt


class Vector:
    @classmethod
    def dot(cls, first, second):
        return first.x * second.x + first.y * second.y

    @property
    def length(self):
        return sqrt(self.x * self.x + self.y * self. y)

    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __add__(self, other):
        return Vector(self.x + other.x, self.y + other.y)

    def __sub__(self, other):
        return Vector(self.x - other.x, self.y - other.y)

    def __mul__(self, other):
        return Vector.dot(self, other)

    def __str__(self):
        return '({0}, {1})'.format(self.x, self.y)

    def __eq__(self, other):
        return (isinstance(other, self.__class__) and
                self.x == other.x and self.y == other.y)

    def dot(self, other):
        return Vector.dot(self, other)

v1 = Vector(1, 2)
v2 = Vector(2, 3)

assert v1 + v2 == Vector(3, 5)
assert v1 - v2 == Vector(-1, -1)
print v1 * v2 == 8
# assert v1.dot(v2) == 8
# assert Vector.dot(v1, v2) == 8