Pythonスタイルオブジェクトを作成するためのPython組み込みメソッド
この記事では、Pythonの組み込みメソッドを使用して2次元のベクトルオブジェクトと多次元のベクトルオブジェクトを作成し、組み込みのメソッドを実装して、それらの動作にPythonスタイルを設定します。
2次元ベクトルオブジェクトの例(特定のコードについては、「スムーズPython」の第9章を参照してください)
"""
A 2-dimensional vector class
>>> v1 = Vector2d(3, 4)
>>> print(v1.x, v1.y)
3.0 4.0
>>> 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'd\\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>'
# BEGIN VECTOR2D_V3_DEMO
Tests of `x` and `y` read-only properties:
>>> v1.x, v1.y
(3.0, 4.0)
>>> v1.x = 123
Traceback (most recent call last):
...
AttributeError: can't set attribute
# END VECTOR2D_V3_HASH_DEMO
Tests of hashing:
# BEGIN VECTOR2D_V3_HASH_DEMO
>>> v1 = Vector2d(3, 4)
>>> v2 = Vector2d(3.1, 4.2)
>>> hash(v1), hash(v2)
(7, 384307168202284039)
>>> len(set([v1, v2]))
2
# END VECTOR2D_V3_DEMO
"""
from array import array
import math
# BEGIN VECTOR2D_V3_PROP
class Vector2d:
typecode = 'd'
def __init__(self, x, y):
self.__x = float(x) # <1>
self.__y = float(y)
@property # <2>
def x(self): # <3>
return self.__x # <4>
@property # <5>
def y(self):
return self.__y
def __iter__(self):
return (i for i in (self.x, self.y)) # <6>
# remaining methods follow (omitted in book listing)
# END VECTOR2D_V3_PROP
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([ord(self.typecode)]) +
bytes(array(self.typecode, self)))
def __eq__(self, other):
return tuple(self) == tuple(other)
# BEGIN VECTOR_V3_HASH
def __hash__(self):
return hash(self.x) ^ hash(self.y)
# END VECTOR_V3_HASH
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, fmt_spec=''):
if fmt_spec.endswith('p'):
fmt_spec = fmt_spec[:-1]
coords = (abs(self), self.angle())
outer_fmt = '<{}, {}>'
else:
coords = self
outer_fmt = '({}, {})'
components = (format(c, fmt_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)
多次元ベクトルオブジェクトの例(特定のコードについては、「スムーズPython」の第10章を参照してください)
# BEGIN VECTOR_V5
"""
A multi-dimensional ``Vector`` class, take 5
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: 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 CPython 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>'
"""
from array import array
import reprlib
import math
import numbers
import functools
import operator
import itertools # <1>
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))
def __eq__(self, other):
return (len(self) == len(other) and
all(a == b for a, b in zip(self, other)))
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 __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): # <2>
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): # <3>
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()) # <4>
outer_fmt = '<{}>' # <5>
else:
coords = self
outer_fmt = '({})' # <6>
components = (format(c, fmt_spec) for c in coords) # <7>
return outer_fmt.format(', '.join(components)) # <8>
@classmethod
def frombytes(cls, octets):
typecode = chr(octets[0])
memv = memoryview(octets[1:]).cast(typecode)
return cls(memv)
# END VECTOR_V5