complete draft: update from Atlas

15-more-types/lotto/generic_lotto.py

@@ -0,0 +1,29 @@
+import random
+
+from collections.abc import Iterable
+from typing import TypeVar, Generic
+
+from tombola import Tombola
+
+T = TypeVar('T')
+
+class LottoBlower(Tombola, Generic[T]):  # <1>
+
+    def __init__(self, items: Iterable[T]) -> None:  # <2>
+        self._balls = list[T](items)
+
+    def load(self, items: Iterable[T]) -> None:  # <3>
+        self._balls.extend(items)
+
+    def pick(self) -> T:  # <4>
+        try:
+            position = random.randrange(len(self._balls))
+        except ValueError:
+            raise LookupError('pick from empty LottoBlower')
+        return self._balls.pop(position)
+
+    def loaded(self) -> bool:  # <5>
+        return bool(self._balls)
+
+    def inspect(self) -> tuple[T, ...]:  # <6>
+        return tuple(self._balls)

15-more-types/lotto/generic_lotto_demo.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python3
+
+from typing import TYPE_CHECKING
+
+# tag::LOTTO_USE[]
+from generic_lotto import LottoBlower
+
+machine = LottoBlower[int](range(1, 11))  # <1>
+
+first = machine.pick()  # <2>
+remain = machine.inspect()  # <3>
+# end::LOTTO_USE[]
+
+expected = set(i for i in range(1, 11) if i != first)
+
+assert set(remain) == expected
+
+print('picked:', first)
+print('remain:', remain)
+
+if TYPE_CHECKING:
+    reveal_type(first)
+    # Revealed type is 'builtins.int*'
+if TYPE_CHECKING:
+    reveal_type(remain)
+    # Revealed type is 'builtins.tuple[builtins.int*]'
+
+

15-more-types/lotto/generic_lotto_errors.py

@@ -0,0 +1,18 @@
+from generic_lotto import LottoBlower
+
+machine = LottoBlower[int]([1, .2])
+## error: List item 1 has incompatible type "float";  # <1>
+##        expected "int"
+
+machine = LottoBlower[int](range(1, 11))
+
+machine.load('ABC')
+## error: Argument 1 to "load" of "LottoBlower"  # <2>
+##        has incompatible type "str";
+##        expected "Iterable[int]"
+## note:  Following member(s) of "str" have conflicts:
+## note:      Expected:
+## note:          def __iter__(self) -> Iterator[int]
+## note:      Got:
+## note:          def __iter__(self) -> Iterator[str]
+

15-more-types/lotto/tombola.py

@@ -0,0 +1,34 @@
+# 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(items)
+
+
+# end::TOMBOLA_ABC[]