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"""

A multi-dimensional ``Vector`` class, take 2

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::

# tag::VECTOR_V2_DEMO[]

>>> v7 = Vector(range(7))

>>> v7[-1] # <1>

6.0

>>> v7[1:4] # <2>

Vector([1.0, 2.0, 3.0])

>>> v7[-1:] # <3>

Vector([6.0])

>>> v7[1,2] # <4>

Traceback (most recent call last):

...

TypeError: 'tuple' object cannot be interpreted as an integer

# end::VECTOR_V2_DEMO[]

"""

from array import array

import reprlib

import math

import operator

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))

def __eq__(self, other):

return tuple(self) == tuple(other)

def __abs__(self):

return math.hypot(*self)

def __bool__(self):

return bool(abs(self))

# tag::VECTOR_V2[]

def __len__(self):

return len(self._components)

def __getitem__(self, key):

if isinstance(key, slice): # <1>

cls = type(self) # <2>

return cls(self._components[key]) # <3>

index = operator.index(key) # <4>

return self._components[index] # <5>

# end::VECTOR_V2[]

@classmethod

def frombytes(cls, octets):

typecode = chr(octets[0])

memv = memoryview(octets[1:]).cast(typecode)

return cls(memv)