ch11-24: clean up by @eumiro & sync with Atlas

13-protocol-abc/README.rst

@@ -0,0 +1,4 @@
+Sample code for Chapter 11 - "Interfaces, protocols and ABCs"
+
+From the book "Fluent Python" by Luciano Ramalho (O'Reilly, 2015)
+http://shop.oreilly.com/product/0636920032519.do

13-protocol-abc/bingo.py

@@ -0,0 +1,28 @@
+# tag::TOMBOLA_BINGO[]
+
+import random
+
+from tombola import Tombola
+
+
+class BingoCage(Tombola):  # <1>
+
+    def __init__(self, items):
+        self._randomizer = random.SystemRandom()  # <2>
+        self._items = []
+        self.load(items)  # <3>
+
+    def load(self, items):
+        self._items.extend(items)
+        self._randomizer.shuffle(self._items)  # <4>
+
+    def pick(self):  # <5>
+        try:
+            return self._items.pop()
+        except IndexError:
+            raise LookupError('pick from empty BingoCage')
+
+    def __call__(self):  # <6>
+        self.pick()
+
+# end::TOMBOLA_BINGO[]

13-protocol-abc/double/double_object.py

@@ -0,0 +1,2 @@
+def double(x: object) -> object:
+    return x * 2

13-protocol-abc/double/double_protocol.py

@@ -0,0 +1,11 @@
+from typing import TypeVar, Protocol
+
+T = TypeVar('T')  # <1>
+
+class Repeatable(Protocol):
+    def __mul__(self: T, repeat_count: int) -> T: ...  # <2>
+
+RT = TypeVar('RT', bound=Repeatable)  # <3>
+
+def double(x: RT) -> RT:  # <4>
+    return x * 2

13-protocol-abc/double/double_sequence.py

@@ -0,0 +1,6 @@
+from collections import abc
+from typing import Any
+
+def double(x: abc.Sequence) -> Any:
+    return x * 2
+

13-protocol-abc/double/double_test.py

@@ -0,0 +1,56 @@
+from typing import TYPE_CHECKING
+import pytest
+from double_protocol import double
+
+def test_double_int() -> None:
+    given = 2
+    result = double(given)
+    assert result == given * 2
+    if TYPE_CHECKING:
+        reveal_type(given)
+        reveal_type(result)
+
+
+def test_double_str() -> None:
+    given = 'A'
+    result = double(given)
+    assert result == given * 2
+    if TYPE_CHECKING:
+        reveal_type(given)
+        reveal_type(result)
+
+
+def test_double_fraction() -> None:
+    from fractions import Fraction
+    given = Fraction(2, 5)
+    result = double(given)
+    assert result == given * 2
+    if TYPE_CHECKING:
+        reveal_type(given)
+        reveal_type(result)
+
+
+def test_double_array() -> None:
+    from array import array
+    given = array('d', [1.0, 2.0, 3.14])
+    result = double(given)
+    if TYPE_CHECKING:
+        reveal_type(given)
+        reveal_type(result)
+
+
+def test_double_nparray() -> None:
+    import numpy as np  # type: ignore
+    given = np.array([[1, 2], [3, 4]])
+    result = double(given)
+    comparison = result == given * 2
+    assert comparison.all()
+    if TYPE_CHECKING:
+        reveal_type(given)
+        reveal_type(result)
+
+
+def test_double_none() -> None:
+    given = None
+    with pytest.raises(TypeError):
+        result = double(given)

13-protocol-abc/drum.py

@@ -0,0 +1,17 @@
+from random import shuffle
+
+from tombola import Tombola
+
+
+class TumblingDrum(Tombola):
+
+    def __init__(self, iterable):
+        self._balls = []
+        self.load(iterable)
+
+    def load(self, iterable):
+        self._balls.extend(iterable)
+        shuffle(self._balls)
+
+    def pick(self):
+        return self._balls.pop()

13-protocol-abc/frenchdeck2.py

@@ -0,0 +1,26 @@
+import collections
+
+Card = collections.namedtuple('Card', ['rank', 'suit'])
+
+class FrenchDeck2(collections.MutableSequence):
+    ranks = [str(n) for n in range(2, 11)] + list('JQKA')
+    suits = 'spades diamonds clubs hearts'.split()
+
+    def __init__(self):
+        self._cards = [Card(rank, suit) for suit in self.suits
+                                        for rank in self.ranks]
+
+    def __len__(self):
+        return len(self._cards)
+
+    def __getitem__(self, position):
+        return self._cards[position]
+
+    def __setitem__(self, position, value):  # <1>
+        self._cards[position] = value
+
+    def __delitem__(self, position):  # <2>
+        del self._cards[position]
+
+    def insert(self, position, value):  # <3>
+        self._cards.insert(position, value)

13-protocol-abc/lotto.py

@@ -0,0 +1,30 @@
+# tag::LOTTERY_BLOWER[]
+
+import random
+
+from tombola import Tombola
+
+
+class LotteryBlower(Tombola):
+
+    def __init__(self, iterable):
+        self._balls = list(iterable)  # <1>
+
+    def load(self, iterable):
+        self._balls.extend(iterable)
+
+    def pick(self):
+        try:
+            position = random.randrange(len(self._balls))  # <2>
+        except ValueError:
+            raise LookupError('pick from empty BingoCage')
+        return self._balls.pop(position)  # <3>
+
+    def loaded(self):  # <4>
+        return bool(self._balls)
+
+    def inspect(self):  # <5>
+        return tuple(sorted(self._balls))
+
+
+# end::LOTTERY_BLOWER[]

13-protocol-abc/tombola.py

@@ -0,0 +1,35 @@
+# tag::TOMBOLA_ABC[]
+
+import abc
+
+class Tombola(abc.ABC):  # <1>
+
+    @abc.abstractmethod
+    def load(self, iterable):  # <2>
+        """Add items from an iterable."""
+
+    @abc.abstractmethod
+    def pick(self):  # <3>
+        """Remove item at random, returning it.
+
+        This method should raise `LookupError` when the instance is empty.
+        """
+
+    def loaded(self):  # <4>
+        """Return `True` if there's at least 1 item, `False` otherwise."""
+        return bool(self.inspect())  # <5>
+
+
+    def inspect(self):
+        """Return a sorted tuple with the items currently inside."""
+        items = []
+        while True:  # <6>
+            try:
+                items.append(self.pick())
+            except LookupError:
+                break
+        self.load(items)  # <7>
+        return tuple(sorted(items))
+
+
+# end::TOMBOLA_ABC[]

13-protocol-abc/tombola_runner.py

@@ -0,0 +1,36 @@
+# tag::TOMBOLA_RUNNER[]
+import doctest
+
+from tombola import Tombola
+
+# modules to test
+import bingo, lotto, tombolist, drum  # <1>
+
+TEST_FILE = 'tombola_tests.rst'
+TEST_MSG = '{0:16} {1.attempted:2} tests, {1.failed:2} failed - {2}'
+
+
+def main(argv):
+    verbose = '-v' in argv
+    real_subclasses = Tombola.__subclasses__()  # <2>
+    virtual_subclasses = list(Tombola._abc_registry)  # <3>
+
+    for cls in real_subclasses + virtual_subclasses:  # <4>
+        test(cls, verbose)
+
+
+def test(cls, verbose=False):
+
+    res = doctest.testfile(
+            TEST_FILE,
+            globs={'ConcreteTombola': cls},  # <5>
+            verbose=verbose,
+            optionflags=doctest.REPORT_ONLY_FIRST_FAILURE)
+    tag = 'FAIL' if res.failed else 'OK'
+    print(TEST_MSG.format(cls.__name__, res, tag))  # <6>
+
+
+if __name__ == '__main__':
+    import sys
+    main(sys.argv)
+# end::TOMBOLA_RUNNER[]

13-protocol-abc/tombola_subhook.py

@@ -0,0 +1,64 @@
+"""
+Variation of ``tombola.Tombola`` implementing ``__subclasshook__``.
+
+Tests with simple classes::
+
+    >>> Tombola.__subclasshook__(object)
+    NotImplemented
+    >>> class Complete:
+    ...     def __init__(): pass
+    ...     def load(): pass
+    ...     def pick(): pass
+    ...     def loaded(): pass
+    ...
+    >>> Tombola.__subclasshook__(Complete)
+    True
+    >>> issubclass(Complete, Tombola)
+
+"""
+
+
+from abc import ABC, abstractmethod
+from inspect import getmembers, isfunction
+
+
+class Tombola(ABC):  # <1>
+
+    @abstractmethod
+    def __init__(self, iterable):  # <2>
+        """New instance is loaded from an iterable."""
+
+    @abstractmethod
+    def load(self, iterable):
+        """Add items from an iterable."""
+
+    @abstractmethod
+    def pick(self):  # <3>
+        """Remove item at random, returning it.
+
+        This method should raise `LookupError` when the instance is empty.
+        """
+
+    def loaded(self):  # <4>
+        try:
+            item = self.pick()
+        except LookupError:
+            return False
+        else:
+            self.load([item])  # put it back
+            return True
+
+    @classmethod
+    def __subclasshook__(cls, other_cls):
+        if cls is Tombola:
+            interface_names = function_names(cls)
+            found_names = set()
+            for a_cls in other_cls.__mro__:
+                found_names |= function_names(a_cls)
+            if found_names >= interface_names:
+                return True
+        return NotImplemented
+
+
+def function_names(obj):
+    return {name for name, _ in getmembers(obj, isfunction)}

13-protocol-abc/tombola_tests.rst

@@ -0,0 +1,82 @@
+==============
+Tombola tests
+==============
+
+Every concrete subclass of Tombola should pass these tests.
+
+
+Create and load instance from iterable::
+
+    >>> balls = list(range(3))
+    >>> globe = ConcreteTombola(balls)
+    >>> globe.loaded()
+    True
+    >>> globe.inspect()
+    (0, 1, 2)
+
+
+Pick and collect balls::
+
+    >>> picks = []
+    >>> picks.append(globe.pick())
+    >>> picks.append(globe.pick())
+    >>> picks.append(globe.pick())
+
+
+Check state and results::
+
+    >>> globe.loaded()
+    False
+    >>> sorted(picks) == balls
+    True
+
+
+Reload::
+
+    >>> globe.load(balls)
+    >>> globe.loaded()
+    True
+    >>> picks = [globe.pick() for i in balls]
+    >>> globe.loaded()
+    False
+
+
+Check that `LookupError` (or a subclass) is the exception
+thrown when the device is empty::
+
+    >>> globe = ConcreteTombola([])
+    >>> try:
+    ...     globe.pick()
+    ... except LookupError as exc:
+    ...     print('OK')
+    OK
+
+
+Load and pick 100 balls to verify that they all come out::
+
+    >>> balls = list(range(100))
+    >>> globe = ConcreteTombola(balls)
+    >>> picks = []
+    >>> while globe.inspect():
+    ...     picks.append(globe.pick())
+    >>> len(picks) == len(balls)
+    True
+    >>> set(picks) == set(balls)
+    True
+
+
+Check that the order has changed and is not simply reversed::
+
+    >>> picks != balls
+    True
+    >>> picks[::-1] != balls
+    True
+
+Note: the previous 2 tests have a *very* small chance of failing
+even if the implementation is OK. The probability of the 100
+balls coming out, by chance, in the order they were inspect is
+1/100!, or approximately 1.07e-158. It's much easier to win the
+Lotto or to become a billionaire working as a programmer.
+
+THE END
+

13-protocol-abc/tombolist.py

@@ -0,0 +1,23 @@
+from random import randrange
+
+from tombola import Tombola
+
+@Tombola.register  # <1>
+class TomboList(list):  # <2>
+
+    def pick(self):
+        if self:  # <3>
+            position = randrange(len(self))
+            return self.pop(position)  # <4>
+        else:
+            raise LookupError('pop from empty TomboList')
+
+    load = list.extend  # <5>
+
+    def loaded(self):
+        return bool(self)  # <6>
+
+    def inspect(self):
+        return tuple(sorted(self))
+
+# Tombola.register(TomboList)  # <7>

13-protocol-abc/typing/randompick.py

@@ -0,0 +1,5 @@
+from typing import Protocol, runtime_checkable, Any
+
+@runtime_checkable
+class RandomPicker(Protocol):
+    def pick(self) -> Any: ...

13-protocol-abc/typing/randompick_test.py

@@ -0,0 +1,25 @@
+import random
+from typing import Any, Iterable, TYPE_CHECKING
+
+from randompick import RandomPicker  # <1>
+
+class SimplePicker():  # <2>
+    def __init__(self, items: Iterable) -> None:
+        self._items = list(items)
+        random.shuffle(self._items)
+
+    def pick(self) -> Any:  # <3>
+        return self._items.pop()
+
+def test_isinstance() -> None:  # <4>
+    popper = SimplePicker([1])
+    assert isinstance(popper, RandomPicker)
+
+def test_item_type() -> None:  # <5>
+    items = [1, 2]
+    popper = SimplePicker(items)
+    item = popper.pick()
+    assert item in items
+    if TYPE_CHECKING:
+        reveal_type(item)  # <6>
+    assert isinstance(item, int)

13-protocol-abc/typing/randompickload.py

@@ -0,0 +1,6 @@
+from typing import Protocol, runtime_checkable, Any, Iterable
+from randompick import RandomPicker
+
+@runtime_checkable  # <1>
+class LoadableRandomPicker(RandomPicker, Protocol):  # <2>
+    def load(self, Iterable) -> None: ...  # <3>

13-protocol-abc/typing/randompickload_test.py

@@ -0,0 +1,32 @@
+import random
+from typing import Any, Iterable, TYPE_CHECKING
+
+from randompickload import LoadableRandomPicker
+
+class SimplePicker():
+    def __init__(self, items: Iterable) -> None:
+        self._items = list(items)
+        random.shuffle(self._items)
+
+    def pick(self) -> Any:
+        return self._items.pop()
+
+class LoadablePicker():  # <1>
+    def __init__(self, items: Iterable) -> None:
+        self.load(items)
+
+    def pick(self) -> Any:  # <2>
+        return self._items.pop()
+
+    def load(self, items: Iterable) -> Any:  # <3>
+        self._items = list(items)
+        random.shuffle(self._items)
+
+def test_isinstance() -> None:  # <4>
+    popper = LoadablePicker([1])
+    assert isinstance(popper, LoadableRandomPicker)
+
+def test_isinstance_not() -> None:  # <5>
+    popper = SimplePicker([1])
+    assert not isinstance(popper, LoadableRandomPicker)
+

13-protocol-abc/typing/vector2d_v4.py

@@ -0,0 +1,172 @@
+"""
+A two-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>'
+
+
+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
+
+
+Tests of hashing:
+
+    >>> v1 = Vector2d(3, 4)
+    >>> v2 = Vector2d(3.1, 4.2)
+    >>> hash(v1), hash(v2)
+    (7, 384307168202284039)
+    >>> len(set([v1, v2]))
+    2
+
+Converting to/from a ``complex``:
+# tag::VECTOR2D_V4_DEMO[]
+    >>> from typing import SupportsComplex
+    >>> v3 = Vector2d(1.5, 2.5)
+    >>> isinstance(v3, SupportsComplex)  # <1>
+    True
+    >>> complex(v3)  # <2>
+    (1.5+2.5j)
+    >>> Vector2d.fromcomplex(4+5j)  # <3>
+    Vector2d(4.0, 5.0)
+
+# end::VECTOR2D_V4_DEMO[]
+"""
+
+from array import array
+import math
+
+class Vector2d:
+    typecode = 'd'
+
+    def __init__(self, x, y):
+        self.__x = float(x)
+        self.__y = float(y)
+
+    @property
+    def x(self):
+        return self.__x
+
+    @property
+    def y(self):
+        return self.__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([ord(self.typecode)]) +
+                bytes(array(self.typecode, self)))
+
+    def __eq__(self, other):
+        return tuple(self) == tuple(other)
+
+    def __hash__(self):
+        return hash(self.x) ^ hash(self.y)
+
+    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)
+
+# tag::VECTOR2D_V4_COMPLEX[]
+    def __complex__(self):
+        return complex(self.x, self.y)
+
+    @classmethod
+    def fromcomplex(cls, datum):
+        return Vector2d(datum.real, datum.imag)  # <1>
+# end::VECTOR2D_V4_COMPLEX[]

13-protocol-abc/typing/vector2d_v4_test.py

@@ -0,0 +1,56 @@
+from typing import SupportsComplex, SupportsAbs, Tuple
+from typing import TYPE_CHECKING
+import math
+import pytest
+
+from vector2d_v4 import Vector2d
+
+def test_SupportsComplex_subclass() -> None:
+    assert issubclass(Vector2d, SupportsComplex)
+
+def test_SupportsComplex_isinstance() -> None:
+    v = Vector2d(3, 4)
+    assert isinstance(v, SupportsComplex)
+    c = complex(v)
+    assert c == 3 + 4j
+
+def test_SupportsAbs_subclass() -> None:
+    assert issubclass(Vector2d, SupportsAbs)
+
+def test_SupportsAbs_isinstance() -> None:
+    v = Vector2d(3, 4)
+    assert isinstance(v, SupportsAbs)
+    r = abs(v)
+    assert r == 5.0
+    if TYPE_CHECKING:
+        reveal_type(r)  # Revealed type is 'Any'
+
+def magnitude(v: SupportsAbs) -> float:
+    return abs(v)
+
+def test_SupportsAbs_Vector2d_argument() -> None:
+    assert magnitude(Vector2d(3, 4)) == 5.0
+
+def test_SupportsAbs_object_argument() -> None:
+    with pytest.raises(TypeError):
+        magnitude(object())
+        # mypy error:
+        # Argument 1 to "magnitude" has incompatible type "object"; expected "SupportsAbs[Any]"
+
+def polar(datum: SupportsComplex) -> Tuple[float, float]:
+    c = complex(datum)
+    return abs(c), math.atan2(c.imag, c.real)
+
+def test_SupportsComplex_Vector2d_argument() -> None:
+    assert polar(Vector2d(2, 0)) == (2, 0)
+    expected = (2, math.pi / 2)
+    result = polar(Vector2d(0, 2))
+    assert math.isclose(result[0], expected[0])
+    assert math.isclose(result[1], expected[1])
+
+def test_SupportsComplex_complex_argument() -> None:
+    assert polar(complex(2, 0)) == (2, 0)
+    expected = (2, math.pi / 2)
+    result = polar(complex(0, 2))
+    assert math.isclose(result[0], expected[0])
+    assert math.isclose(result[1], expected[1])

13-protocol-abc/typing/vector2d_v5.py

@@ -0,0 +1,174 @@
+from __future__ import annotations
+
+"""
+A two-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>'
+
+
+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
+
+
+Tests of hashing:
+
+    >>> v1 = Vector2d(3, 4)
+    >>> v2 = Vector2d(3.1, 4.2)
+    >>> hash(v1), hash(v2)
+    (7, 384307168202284039)
+    >>> len(set([v1, v2]))
+    2
+
+Converting to/from a ``complex``:
+
+    >>> from typing import SupportsComplex
+    >>> v3 = Vector2d(1.5, 2.5)
+    >>> isinstance(v3, SupportsComplex)  # <1>
+    True
+    >>> complex(v3)  # <2>
+    (1.5+2.5j)
+    >>> Vector2d.fromcomplex(4+5j)  # <3>
+    Vector2d(4.0, 5.0)
+"""
+
+from array import array
+import math
+from typing import SupportsComplex, Iterator
+
+class Vector2d:
+    typecode = 'd'
+
+    def __init__(self, x, y) -> None:
+        self.__x = float(x)
+        self.__y = float(y)
+
+    @property
+    def x(self) -> float:
+        return self.__x
+
+    @property
+    def y(self) -> float:
+        return self.__y
+
+    def __iter__(self) -> Iterator[float]:
+        return (i for i in (self.x, self.y))
+
+    def __repr__(self) -> str:
+        class_name = type(self).__name__
+        return '{}({!r}, {!r})'.format(class_name, *self)
+
+    def __str__(self) -> str:
+        return str(tuple(self))
+
+    def __bytes__(self) -> bytes:
+        return (bytes([ord(self.typecode)]) +
+                bytes(array(self.typecode, self)))
+
+    def __eq__(self, other) -> bool:
+        return tuple(self) == tuple(other)
+
+    def __hash__(self) -> int:
+        return hash(self.x) ^ hash(self.y)
+
+    def __bool__(self) -> bool:
+        return bool(abs(self))
+
+    def angle(self) -> float:
+        return math.atan2(self.y, self.x)
+
+    def __format__(self, fmt_spec='') -> str:
+        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) -> Vector2d:
+        typecode = chr(octets[0])
+        memv = memoryview(octets[1:]).cast(typecode)
+        return cls(*memv)
+
+# tag::VECTOR2D_V5_COMPLEX[]
+    def __abs__(self) -> float:  # <1>
+        return math.hypot(self.x, self.y)
+
+    def __complex__(self) -> complex:  # <2>
+        return complex(self.x, self.y)
+
+    @classmethod
+    def fromcomplex(cls, datum: SupportsComplex) -> Vector2d:  # <3>
+        c = complex(datum)  # <4>
+        return Vector2d(c.real, c.imag)
+# end::VECTOR2D_V5_COMPLEX[]

13-protocol-abc/typing/vector2d_v5_test.py

@@ -0,0 +1,35 @@
+from vector2d_v5 import Vector2d
+from typing import SupportsComplex, SupportsAbs, TYPE_CHECKING
+
+import pytest
+
+
+def test_SupportsComplex_subclass() -> None:
+    assert issubclass(Vector2d, SupportsComplex)
+
+def test_SupportsComplex_isinstance() -> None:
+    v = Vector2d(3, 4)
+    assert isinstance(v, SupportsComplex)
+    c = complex(v)
+    assert c == 3 + 4j
+
+def test_SupportsAbs_subclass() -> None:
+    assert issubclass(Vector2d, SupportsAbs)
+
+def test_SupportsAbs_isinstance() -> None:
+    v = Vector2d(3, 4)
+    assert isinstance(v, SupportsAbs)
+    r = abs(v)
+    assert r == 5.0
+    if TYPE_CHECKING:
+        reveal_type(r)  # Revealed type is 'builtins.float*'
+
+def magnitude(v: SupportsAbs) -> float:
+    return abs(v)
+
+def test_SupportsAbs_Vector2d_argument() -> None:
+    assert 5.0 == magnitude(Vector2d(3, 4))
+
+def test_SupportsAbs_object_argument() -> None:
+    with pytest.raises(TypeError):
+        assert 5.0 == magnitude(object())