《流畅的Python》第二版 第11章

from array import array
import math


class Vector2d:
    __match_args__ = ('x', 'y')
    typecode = 'd'

    def __init__(self, x, y):
        self.__x = float(x)
        self.__y = float(y)

    @property
    def x(self):
        return self.__x


    @property
    def y(self):
        return self.__y


    def __iter__(self):
        return (i for i in (self.x, self.y))


    def __repr__(self):
        cls_name = type(self).__name__
        return "{}({!r},{!r})".format(cls_name, *self)


    def __str__(self):
        return str(tuple(self))


    def __bytes__(self):
        return (bytes([ord(self.typecode)]) + bytes(array(self.typecode, self)))


    def __eq__(self, other):
        return tuple(self) == tuple(other)


    def __hash__(self):
        return hash((self.x, self.y))


    def __abs__(self):
        return math.hypot(self.x, self.y)


    def __bool__(self):
        return bool(abs(self))


    def angle(self):
        return math.atan2(self.y, self.x)

    def __format__(self, format_spec = ''):
        if format_spec.endswith('p'):
            format_spec = format_spec[:-1]
            coords = (abs(self), self.angle())  #confirm this
            outer_fmt = '<{}, {}>'
        else:
            coords = self
            outer_fmt = '({}, {})'

        components = (format(c, format_spec) for c in coords)
        return outer_fmt.format(*components)


    @classmethod
    def frombytes(cls, octets):
        typecode = chr(octets[0])
        memv = memoryview(octets[1:]).cast(typecode)
        return cls(*memv)