last example of chapter 9: classes/vector_v5.py
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Luciano Ramalho
@@ -1,155 +1,198 @@
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"""
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A 2-dimensional vector class
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A multi-dimensional ``Vector`` class, take 3
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>>> v1 = Vector(3, 4)
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>>> x, y = v1 #<1>
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A ``Vector`` is built from an iterable of numbers::
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>>> Vector([3.1, 4.2])
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Vector([3.1, 4.2])
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>>> Vector((3, 4, 5))
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Vector([3.0, 4.0, 5.0])
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>>> Vector(range(10))
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Vector([0.0, 1.0, 2.0, 3.0, 4.0, ...])
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Tests with 2-dimensions (same results as ``vector2d_v1.py``)::
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>>> v1 = Vector([3, 4])
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>>> x, y = v1
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>>> x, y
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(3.0, 4.0)
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>>> v1 #<2>
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Vector(3.0, 4.0)
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>>> v1_clone = eval(repr(v1)) #<3>
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>>> v1
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Vector([3.0, 4.0])
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>>> v1_clone = eval(repr(v1))
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>>> v1 == v1_clone
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True
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>>> print(v1) #<4>
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>>> print(v1)
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(3.0, 4.0)
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>>> octets = bytes(v1) #<5>
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>>> octets = bytes(v1)
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>>> octets
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b'\\x00\\x00\\x00\\x00\\x00\\x00\\x08@\\x00\\x00\\x00\\x00\\x00\\x00\\x10@'
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>>> abs(v1) #<6>
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>>> abs(v1)
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5.0
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>>> bool(v1), bool(Vector(0, 0)) #<7>
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>>> bool(v1), bool(Vector([0, 0]))
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(True, False)
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Test of .frombytes() class method:
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Test of ``.frombytes()`` class method:
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>>> v1_clone = Vector.frombytes(bytes(v1))
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>>> v1_clone
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Vector(3.0, 4.0)
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Vector([3.0, 4.0])
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>>> v1 == v1_clone
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True
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Tests of ``format()`` with Cartesian coordinates:
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>>> format(v1)
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'(3.0, 4.0)'
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>>> format(v1, '.2f')
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'(3.00, 4.00)'
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>>> format(v1, '.3e')
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'(3.000e+00, 4.000e+00)'
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Tests with 3-dimensions::
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Tests of the ``angle`` method::
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>>> Vector(0, 0).angle()
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0.0
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>>> Vector(1, 0).angle()
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0.0
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>>> epsilon = 10**-8
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>>> abs(Vector(0, 1).angle() - math.pi/2) < epsilon
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>>> v1 = Vector([3, 4, 5])
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>>> x, y, z = v1
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>>> x, y, z
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(3.0, 4.0, 5.0)
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>>> v1
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Vector([3.0, 4.0, 5.0])
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>>> v1_clone = eval(repr(v1))
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>>> v1 == v1_clone
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True
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>>> abs(Vector(1, 1).angle() - math.pi/4) < epsilon
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>>> print(v1)
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(3.0, 4.0, 5.0)
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>>> abs(v1) # doctest:+ELLIPSIS
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7.071067811...
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>>> bool(v1), bool(Vector([0, 0, 0]))
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(True, False)
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Tests with many dimensions::
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>>> v7 = Vector(range(7))
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>>> v7
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Vector([0.0, 1.0, 2.0, 3.0, 4.0, ...])
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>>> abs(v7) # doctest:+ELLIPSIS
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9.53939201...
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Test of ``.__bytes__`` and ``.frombytes()`` methods::
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>>> v1 = Vector([3, 4, 5])
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>>> v1_clone = Vector.frombytes(bytes(v1))
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>>> v1_clone
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Vector([3.0, 4.0, 5.0])
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>>> v1 == v1_clone
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True
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Tests of ``format()`` with polar coordinates:
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Tests of sequence behavior::
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>>> format(Vector(1, 1), 'p') # doctest:+ELLIPSIS
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'<1.414213..., 0.785398...>'
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>>> format(Vector(1, 1), '.3ep')
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'<1.414e+00, 7.854e-01>'
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>>> format(Vector(1, 1), '0.5fp')
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'<1.41421, 0.78540>'
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>>> v1 = Vector([3, 4, 5])
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>>> len(v1)
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3
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>>> v1[0], v1[len(v1)-1], v1[-1]
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(3.0, 5.0, 5.0)
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# BEGIN VECTOR_V3_DEMO
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Test of `x` and `y` read-only properties:
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>>> v1.x, v1.y
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(3.0, 4.0)
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>>> v1.x = 123
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Test of slicing::
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>>> v7 = Vector(range(7))
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>>> v7[-1]
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6.0
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>>> v7[1:4]
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Vector([1.0, 2.0, 3.0])
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>>> v7[-1:]
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Vector([6.0])
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>>> v7[1,2]
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Traceback (most recent call last):
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...
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AttributeError: can't set attribute
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# END VECTOR_V3_HASH_DEMO
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# BEGIN VECTOR_V3_HASH_DEMO
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>>> v1 = Vector(3, 4)
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>>> v2 = Vector(3.1, 4.2)
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>>> hash(v1), hash(v2)
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(7, 384307168202284039)
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>>> len(set([v1, v2]))
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2
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TypeError: Vector indices must be integers
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# END VECTOR_V3_DEMO
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Tests of dynamic attribute access::
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>>> v7 = Vector(range(10))
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>>> v7.x
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0.0
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>>> v7.y, v7.z, v7.t, v7.u, v7.v, v7.w
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(1.0, 2.0, 3.0, 4.0, 5.0, 6.0)
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Dynamic attribute lookup failures::
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>>> v7.k
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Traceback (most recent call last):
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...
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AttributeError: 'Vector' object has no attribute 'k'
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>>> v3 = Vector(range(3))
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>>> v3.t
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Traceback (most recent call last):
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...
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AttributeError: 'Vector' object has no attribute 't'
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>>> v3.spam
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Traceback (most recent call last):
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...
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AttributeError: 'Vector' object has no attribute 'spam'
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"""
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from array import array
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import reprlib
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import math
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# BEGIN VECTOR_V3
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class Vector:
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typecode = 'd'
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def __init__(self, x, y):
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self.__x = float(x) # <1>
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self.__y = float(y)
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@property # <2>
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def x(self): # <3>
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return self.__x # <4>
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@property # <5>
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def y(self):
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return self.__y
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def __init__(self, components):
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self._components = array(self.typecode, components)
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def __iter__(self):
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return (i for i in (self.x, self.y)) # <6>
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# remaining methods follow (omitted in book listing)
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# END VECTOR_V3
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return iter(self._components)
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def __repr__(self):
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return 'Vector({!r}, {!r})'.format(*self)
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components = reprlib.repr(self._components)
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components = components[components.find('['):-1]
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return 'Vector({})'.format(components)
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def __str__(self):
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return str(tuple(self))
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def __bytes__(self):
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return bytes(array(Vector.typecode, self))
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return bytes(self._components)
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def __eq__(self, other):
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return tuple(self) == tuple(other)
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# BEGIN VECTOR_V3_HASH
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def __hash__(self):
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return hash(self.x) ^ hash(self.y)
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# END VECTOR_V3_HASH
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def __abs__(self):
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return math.hypot(self.x, self.y)
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return math.sqrt(sum(x * x for x in self))
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def __bool__(self):
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return bool(abs(self))
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def angle(self):
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return math.atan2(self.y, self.x)
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def __len__(self):
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return len(self._components)
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def __format__(self, fmt_spec=''):
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if fmt_spec.endswith('p'):
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fmt_spec = fmt_spec[:-1]
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coords = (abs(self), self.angle())
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outer_fmt = '<{}, {}>'
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def __getitem__(self, index):
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cls = type(self)
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if isinstance(index, slice):
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return cls(self._components[index])
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elif isinstance(index, int):
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return self._components[index]
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else:
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coords = self
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outer_fmt = '({}, {})'
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components = (format(c, fmt_spec) for c in coords)
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return outer_fmt.format(*components)
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msg = '{.__name__} indices must be integers'
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raise TypeError(msg.format(cls))
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# BEGIN VECTOR_V3
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shortcut_names = 'xyztuvw'
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def __getattr__(self, name):
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cls = type(self) # <1>
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if len(name) == 1: # <2>
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pos = cls.shortcut_names.find(name) # <3>
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if 0 <= pos < len(self._components): # <4>
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return self._components[pos]
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msg = '{.__name__!r} object has no attribute {!r}' # <5>
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raise AttributeError(msg.format(cls, name))
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# END VECTOR_V3
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@classmethod
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def frombytes(cls, octets):
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memv = memoryview(octets).cast(cls.typecode)
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return cls(*memv)
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return cls(memv)
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