第四章 面向对象编程--案例

第零章 学前准备
第一章 数据结构 – 基本数据类型
第一章 数据结构 – 字符串
第一章 数据结构 – 列表、元组和切片
第一章 数据结构 – 字典
第一章 数据结构 – 集合
第一章 – 数组、队列、枚举
第一章 数据结构 – 序列分类
第二章 控制流程
第三章 函数也是对象 – 函数定义以及参数
第三章 函数也是对象 – 高阶函数以及装饰器
第三章 函数也是对象 – lambda 表达式、可调用函数及内置函数
第四章 面向对象编程 – 自定义类、属性、方法和函数
第四章 面向对象编程–魔术方法1
第四章 面向对象编程 – 魔术方法2
第四章 面向对象编程 – 可迭代的对象、迭代器和生成器
第四章 面向对象编程 – 继承、接口
第四章 面向对象编程 – 对象引用
第四章 面向对象编程–案例

---

第四章 面向对象编程–案例

4.6 案例：Vector实例

"""
A multi-dimensional ``Vector`` class, take 8: operator ``==``

A ``Vector`` is built from an iterable of numbers::

    >>> Vector([3.1, 4.2])
    Vector([3.1, 4.2])
    >>> Vector((3, 4, 5))
    Vector([3.0, 4.0, 5.0])
    >>> Vector(range(10))
    Vector([0.0, 1.0, 2.0, 3.0, 4.0, ...])


Tests with 2-dimensions (same results as ``vector2d_v1.py``)::

    >>> v1 = Vector([3, 4])
    >>> x, y = v1
    >>> x, y
    (3.0, 4.0)
    >>> v1
    Vector([3.0, 4.0])
    >>> v1_clone = eval(repr(v1))
    >>> v1 == v1_clone
    True
    >>> print(v1)
    (3.0, 4.0)
    >>> octets = bytes(v1)
    >>> octets
    b'd\\x00\\x00\\x00\\x00\\x00\\x00\\x08@\\x00\\x00\\x00\\x00\\x00\\x00\\x10@'
    >>> abs(v1)
    5.0
    >>> bool(v1), bool(Vector([0, 0]))
    (True, False)


Test of ``.frombytes()`` class method:

    >>> v1_clone = Vector.frombytes(bytes(v1))
    >>> v1_clone
    Vector([3.0, 4.0])
    >>> v1 == v1_clone
    True


Tests with 3-dimensions::

    >>> v1 = Vector([3, 4, 5])
    >>> x, y, z = v1
    >>> x, y, z
    (3.0, 4.0, 5.0)
    >>> v1
    Vector([3.0, 4.0, 5.0])
    >>> v1_clone = eval(repr(v1))
    >>> v1 == v1_clone
    True
    >>> print(v1)
    (3.0, 4.0, 5.0)
    >>> abs(v1)  # doctest:+ELLIPSIS
    7.071067811...
    >>> bool(v1), bool(Vector([0, 0, 0]))
    (True, False)


Tests with many dimensions::

    >>> v7 = Vector(range(7))
    >>> v7
    Vector([0.0, 1.0, 2.0, 3.0, 4.0, ...])
    >>> abs(v7)  # doctest:+ELLIPSIS
    9.53939201...


Test of ``.__bytes__`` and ``.frombytes()`` methods::

    >>> v1 = Vector([3, 4, 5])
    >>> v1_clone = Vector.frombytes(bytes(v1))
    >>> v1_clone
    Vector([3.0, 4.0, 5.0])
    >>> v1 == v1_clone
    True


Tests of sequence behavior::

    >>> v1 = Vector([3, 4, 5])
    >>> len(v1)
    3
    >>> v1[0], v1[len(v1)-1], v1[-1]
    (3.0, 5.0, 5.0)


Test of slicing::

    >>> v7 = Vector(range(7))
    >>> v7[-1]
    6.0
    >>> v7[1:4]
    Vector([1.0, 2.0, 3.0])
    >>> v7[-1:]
    Vector([6.0])
    >>> v7[1,2]
    Traceback (most recent call last):
      ...
    TypeError: 'tuple' object cannot be interpreted as an integer


Tests of dynamic attribute access::

    >>> v7 = Vector(range(10))
    >>> v7.x
    0.0
    >>> v7.y, v7.z, v7.t
    (1.0, 2.0, 3.0)

Dynamic attribute lookup failures::

    >>> v7.k
    Traceback (most recent call last):
      ...
    AttributeError: 'Vector' object has no attribute 'k'
    >>> v3 = Vector(range(3))
    >>> v3.t
    Traceback (most recent call last):
      ...
    AttributeError: 'Vector' object has no attribute 't'
    >>> v3.spam
    Traceback (most recent call last):
      ...
    AttributeError: 'Vector' object has no attribute 'spam'


Tests of hashing::

    >>> v1 = Vector([3, 4])
    >>> v2 = Vector([3.1, 4.2])
    >>> v3 = Vector([3, 4, 5])
    >>> v6 = Vector(range(6))
    >>> hash(v1), hash(v3), hash(v6)
    (7, 2, 1)


Most hash codes of non-integers vary from a 32-bit to 64-bit Python build::

    >>> import sys
    >>> hash(v2) == (384307168202284039 if sys.maxsize > 2**32 else 357915986)
    True


Tests of ``format()`` with Cartesian coordinates in 2D::

    >>> v1 = Vector([3, 4])
    >>> format(v1)
    '(3.0, 4.0)'
    >>> format(v1, '.2f')
    '(3.00, 4.00)'
    >>> format(v1, '.3e')
    '(3.000e+00, 4.000e+00)'


Tests of ``format()`` with Cartesian coordinates in 3D and 7D::

    >>> v3 = Vector([3, 4, 5])
    >>> format(v3)
    '(3.0, 4.0, 5.0)'
    >>> format(Vector(range(7)))
    '(0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0)'


Tests of ``format()`` with spherical coordinates in 2D, 3D and 4D::

    >>> format(Vector([1, 1]), 'h')  # doctest:+ELLIPSIS
    '<1.414213..., 0.785398...>'
    >>> format(Vector([1, 1]), '.3eh')
    '<1.414e+00, 7.854e-01>'
    >>> format(Vector([1, 1]), '0.5fh')
    '<1.41421, 0.78540>'
    >>> format(Vector([1, 1, 1]), 'h')  # doctest:+ELLIPSIS
    '<1.73205..., 0.95531..., 0.78539...>'
    >>> format(Vector([2, 2, 2]), '.3eh')
    '<3.464e+00, 9.553e-01, 7.854e-01>'
    >>> format(Vector([0, 0, 0]), '0.5fh')
    '<0.00000, 0.00000, 0.00000>'
    >>> format(Vector([-1, -1, -1, -1]), 'h')  # doctest:+ELLIPSIS
    '<2.0, 2.09439..., 2.18627..., 3.92699...>'
    >>> format(Vector([2, 2, 2, 2]), '.3eh')
    '<4.000e+00, 1.047e+00, 9.553e-01, 7.854e-01>'
    >>> format(Vector([0, 1, 0, 0]), '0.5fh')
    '<1.00000, 1.57080, 0.00000, 0.00000>'


Unary operator tests::

    >>> v1 = Vector([3, 4])
    >>> abs(v1)
    5.0
    >>> -v1
    Vector([-3.0, -4.0])
    >>> +v1
    Vector([3.0, 4.0])


Basic tests of operator ``+``::

    >>> v1 = Vector([3, 4, 5])
    >>> v2 = Vector([6, 7, 8])
    >>> v1 + v2
    Vector([9.0, 11.0, 13.0])
    >>> v1 + v2 == Vector([3+6, 4+7, 5+8])
    True
    >>> v3 = Vector([1, 2])
    >>> v1 + v3  # short vectors are filled with 0.0 on addition
    Vector([4.0, 6.0, 5.0])


Tests of ``+`` with mixed types::

    >>> v1 + (10, 20, 30)
    Vector([13.0, 24.0, 35.0])
    >>> v2d = Vector2d(1, 2)
    >>> v1 + v2d
    Vector([4.0, 6.0, 5.0])


Tests of ``+`` with mixed types, swapped operands::

    >>> (10, 20, 30) + v1
    Vector([13.0, 24.0, 35.0])
    >>> v2d = Vector2d(1, 2)
    >>> v2d + v1
    Vector([4.0, 6.0, 5.0])


Tests of ``+`` with an unsuitable operand:

    >>> v1 + 1
    Traceback (most recent call last):
      ...
    TypeError: unsupported operand type(s) for +: 'Vector' and 'int'
    >>> v1 + 'ABC'
    Traceback (most recent call last):
      ...
    TypeError: unsupported operand type(s) for +: 'Vector' and 'str'


Basic tests of operator ``*``::

    >>> v1 = Vector([1, 2, 3])
    >>> v1 * 10
    Vector([10.0, 20.0, 30.0])
    >>> 10 * v1
    Vector([10.0, 20.0, 30.0])


Tests of ``*`` with unusual but valid operands::

    >>> v1 * True
    Vector([1.0, 2.0, 3.0])
    >>> from fractions import Fraction
    >>> v1 * Fraction(1, 3)  # doctest:+ELLIPSIS
    Vector([0.3333..., 0.6666..., 1.0])


Tests of ``*`` with unsuitable operands::

    >>> v1 * (1, 2)
    Traceback (most recent call last):
      ...
    TypeError: can't multiply sequence by non-int of type 'Vector'


Tests of operator `==`::

    >>> va = Vector(range(1, 4))
    >>> vb = Vector([1.0, 2.0, 3.0])
    >>> va == vb
    True
    >>> vc = Vector([1, 2])
    >>> v2d = Vector2d(1, 2)
    >>> vc == v2d
    True
    >>> va == (1, 2, 3)
    False


Tests of operator `!=`::

    >>> va != vb
    False
    >>> vc != v2d
    False
    >>> va != (1, 2, 3)
    True

"""

import doctest
from array import array
import reprlib
import math
import numbers
import functools
import operator
import itertools


class Vector:
    typecode = 'd'

    def __init__(self, components):
        self._components = array(self.typecode, components)

    def __iter__(self):
        return iter(self._components)

    def __repr__(self):
        components = reprlib.repr(self._components)
        components = components[components.find('['):-1]
        return f'Vector({
      
      components})'

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

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

# tag::VECTOR_V8_EQ[]
    def __eq__(self, other):
        if isinstance(other, Vector):  # <1>
            return (len(self) == len(other) and
                    all(a == b for a, b in zip(self, other)))
        else:
            return NotImplemented  # <2>
# end::VECTOR_V8_EQ[]

    def __hash__(self):
        hashes = (hash(x) for x in self)
        return functools.reduce(operator.xor, hashes, 0)

    def __abs__(self):
        return math.hypot(*self)

    def __neg__(self):
        return Vector(-x for x in self)

    def __pos__(self):
        return Vector(self)

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

    def __len__(self):
        return len(self._components)

    def __getitem__(self, key):
        if isinstance(key, slice):
            cls = type(self)
            return cls(self._components[key])
        index = operator.index(key)
        return self._components[index]

    __match_args__ = ('x', 'y', 'z', 't')

    def __getattr__(self, name):
        cls = type(self)
        try:
            pos = cls.__match_args__.index(name)
        except ValueError:
            pos = -1
        if 0 <= pos < len(self._components):
            return self._components[pos]
        msg = f'{
      
      cls.__name__!r} object has no attribute {
      
      name!r}'
        raise AttributeError(msg)

    def angle(self, n):
        r = math.hypot(*self[n:])
        a = math.atan2(r, self[n-1])
        if (n == len(self) - 1) and (self[-1] < 0):
            return math.pi * 2 - a
        else:
            return a

    def angles(self):
        return (self.angle(n) for n in range(1, len(self)))

    def __format__(self, fmt_spec=''):
        if fmt_spec.endswith('h'):  # hyperspherical coordinates
            fmt_spec = fmt_spec[:-1]
            coords = itertools.chain([abs(self)],
                                     self.angles())
            outer_fmt = '<{}>'
        else:
            coords = self
            outer_fmt = '({})'
        components = (format(c, fmt_spec) for c in coords)
        return outer_fmt.format(', '.join(components))

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

    def __add__(self, other):
        try:
            pairs = itertools.zip_longest(self, other, fillvalue=0.0)
            return Vector(a + b for a, b in pairs)
        except TypeError:
            return NotImplemented

    def __radd__(self, other):
        return self + other

    def __mul__(self, scalar):
        if isinstance(scalar, numbers.Real):
            return Vector(n * scalar for n in self)
        else:
            return NotImplemented

    def __rmul__(self, scalar):
        return self * scalar

    def __matmul__(self, other):
        try:
            return sum(a * b for a, b in zip(self, other))
        except TypeError:
            return NotImplemented

    def __rmatmul__(self, other):
        return self @ other


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