example-code/13-op-overloading/vector_v8.py at master · fluentpython/example-code

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"""

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)

>>> 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: Vector indices must be integers

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 values 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])

>>> from vector2d_v3 import Vector2d

>>> 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])

>>> from vector2d_v3 import Vector2d

>>> 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])

>>> from vector2d_v3 import Vector2d

>>> 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

"""

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 'Vector({})'.format(components)

def __str__(self):

return str(tuple(self))

def __bytes__(self):

return (bytes([ord(self.typecode)]) +

bytes(self._components))

# BEGIN 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.sqrt(sum(x * x for x in 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, index):

cls = type(self)

if isinstance(index, slice):

return cls(self._components[index])

elif isinstance(index, numbers.Integral):

return self._components[index]

else:

msg = '{.__name__} indices must be integers'

raise TypeError(msg.format(cls))

shortcut_names = 'xyzt'

def __getattr__(self, name):

cls = type(self)

if len(name) == 1:

pos = cls.shortcut_names.find(name)

if 0 <= pos < len(self._components):

return self._components[pos]

msg = '{.__name__!r} object has no attribute {!r}'

raise AttributeError(msg.format(cls, name))

def angle(self, n):

r = math.sqrt(sum(x * x for x in 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

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