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vector2d_v2_fmt_snippet.py

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"""

A 2-dimensional vector class

>>> v1 = Vector2d(3, 4)

>>> x, y = v1

>>> x, y

(3.0, 4.0)

>>> v1

Vector2d(3.0, 4.0)

>>> v1_clone = eval(repr(v1))

>>> v1 == v1_clone

True

>>> print(v1)

(3.0, 4.0)

>>> octets = bytes(v1)

>>> octets

b'\\x00\\x00\\x00\\x00\\x00\\x00\\x08@\\x00\\x00\\x00\\x00\\x00\\x00\\x10@'

>>> abs(v1)

5.0

>>> bool(v1), bool(Vector2d(0, 0))

(True, False)

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

>>> v1_clone = Vector2d.frombytes(bytes(v1))

>>> v1_clone

Vector2d(3.0, 4.0)

>>> v1 == v1_clone

True

Tests of ``format()`` with Cartesian coordinates:

>>> format(v1)

'(3.0, 4.0)'

>>> format(v1, '.2f')

'(3.00, 4.00)'

>>> format(v1, '.3e')

'(3.000e+00, 4.000e+00)'

Tests of the ``angle`` method::

>>> Vector2d(0, 0).angle()

0.0

>>> Vector2d(1, 0).angle()

0.0

>>> epsilon = 10**-8

>>> abs(Vector2d(0, 1).angle() - math.pi/2) < epsilon

True

>>> abs(Vector2d(1, 1).angle() - math.pi/4) < epsilon

True

Tests of ``format()`` with polar coordinates:

>>> format(Vector2d(1, 1), 'p') # doctest:+ELLIPSIS

'<1.414213..., 0.785398...>'

>>> format(Vector2d(1, 1), '.3ep')

'<1.414e+00, 7.854e-01>'

>>> format(Vector2d(1, 1), '0.5fp')

'<1.41421, 0.78540>'

"""

from array import array

import math

class Vector2d:

typecode = 'd'

def __init__(self, x, y):

self.x = float(x)

self.y = float(y)

def __iter__(self):

return (i for i in (self.x, self.y))

def __repr__(self):

class_name = type(self).__name__

return '{}({!r}, {!r})'.format(class_name, *self)

def __str__(self):

return str(tuple(self))

def __bytes__(self):

return bytes(array(Vector2d.typecode, self))

def __eq__(self, other):

return tuple(self) == tuple(other)

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)

# BEGIN VECTOR2D_V2_FORMAT

def __format__(self, fmt_spec=''):

if fmt_spec.endswith('p'): # <1>

fmt_spec = fmt_spec[:-1] # <2>

coords = (abs(self), self.angle()) # <3>

outer_fmt = '<{}, {}>' # <4>

else:

coords = self # <5>

outer_fmt = '({}, {})' # <6>

components = (format(c, fmt_spec) for c in coords) # <7>

return outer_fmt.format(*components) # <8>

# END VECTOR2D_V2_FORMAT

@classmethod

def frombytes(cls, octets):

memv = memoryview(octets).cast(cls.typecode)

return cls(*memv)