added cafeteria example

15-more-types/cafeteria.py

@@ -0,0 +1,82 @@
+from typing import TypeVar, Generic
+
+
+class Beverage:
+    """Any beverage"""
+
+
+class Juice(Beverage):
+    """Any fruit juice"""
+
+
+class OrangeJuice(Juice):
+    """Delicious juice from Brazilian oranges"""
+
+
+BeverageT = TypeVar('BeverageT', covariant=True)
+
+
+class BeverageDispenser(Generic[BeverageT]):
+    def __init__(self, beverage: BeverageT) -> None:
+        self.beverage = beverage
+
+    def dispense(self) -> BeverageT:
+        return self.beverage
+
+
+class Garbage:
+    """Any garbage."""
+
+
+class Biodegradable(Garbage):
+    """Biodegradable garbage."""
+
+
+class Compostable(Biodegradable):
+    """Compostable garbage."""
+
+
+GarbageT = TypeVar('GarbageT', contravariant=True)
+
+
+class TrashCan(Generic[GarbageT]):
+    def put(self, trash) -> None:
+        """Store trash until dumped..."""
+
+
+class Cafeteria:
+    def __init__(
+        self,
+        dispenser: BeverageDispenser[Juice],
+        trash_can: TrashCan[Biodegradable]
+    ):
+        """Initialize..."""
+
+
+beverage_dispenser = BeverageDispenser(Beverage())
+juice_dispenser = BeverageDispenser(Juice())
+orange_juice_dispenser = BeverageDispenser(OrangeJuice())
+
+trash_can: TrashCan[Garbage] = TrashCan()
+bio_can: TrashCan[Biodegradable] = TrashCan()
+compost_can: TrashCan[Compostable] = TrashCan()
+
+arnold_hall = Cafeteria(juice_dispenser, bio_can)
+
+######################## covariance on 1st argument
+arnold_hall = Cafeteria(orange_juice_dispenser, trash_can)
+
+## Argument 1 to "Cafeteria" has
+## incompatible type "BeverageDispenser[Beverage]"
+##          expected "BeverageDispenser[Juice]"
+# arnold_hall = Cafeteria(beverage_dispenser, trash_can)
+
+
+######################## contravariance on 2nd argument
+
+## Argument 2 to "Cafeteria" has
+## incompatible type "TrashCan[Compostable]"
+##          expected "TrashCan[Biodegradable]"
+# arnold_hall = Cafeteria(juice_dispenser, compost_can)
+
+arnold_hall = Cafeteria(juice_dispenser, trash_can)

15-more-types/cafeteria/cafeteria.py

@@ -1,41 +0,0 @@
-from typing import TypeVar, Generic
-
-
-class Beverage:
-    """Any beverage"""
-
-
-class Juice(Beverage):
-    """Any fruit juice"""
-
-
-class OrangeJuice(Juice):
-    """Delicious juice Brazilian oranges"""
-
-
-class Coak(Beverage):
-    """Secret formula with lots of sugar"""
-
-
-BeverageT = TypeVar('BeverageT', bound=Beverage)
-JuiceT = TypeVar('JuiceT', bound=Juice)
-
-
-class BeverageDispenser(Generic[BeverageT]):
-
-    beverage: BeverageT
-
-    def __init__(self, beverage: BeverageT) -> None:
-        self.beverage = beverage
-
-    def dispense(self) -> BeverageT:
-        return self.beverage
-
-
-class JuiceDispenser(BeverageDispenser[JuiceT]):
-    pass
-
-
-class Cafeteria:
-    def __init__(self, dispenser: BeverageDispenser[JuiceT]):
-        self.dispenser = dispenser

15-more-types/cafeteria/cafeteria_demo.py

@@ -1,23 +0,0 @@
-from cafeteria import (
-    Cafeteria,
-    BeverageDispenser,
-    JuiceDispenser,
-    Juice,
-    OrangeJuice,
-    Coak,
-)
-
-orange = OrangeJuice()
-
-orange_dispenser: JuiceDispenser[OrangeJuice] = JuiceDispenser(orange)
-
-juice: Juice = orange_dispenser.dispense()
-
-soda = Coak()
-
-## Value of type variable "JuiceT" of "JuiceDispenser" cannot be "Coak"
-# soda_dispenser = JuiceDispenser(soda)
-
-soda_dispenser = BeverageDispenser(soda)
-
-arnold_hall = Cafeteria(soda_dispenser)

15-more-types/petbox/petbox.py

@@ -10,10 +10,6 @@ class Pet:
     """Domestic animal kept for companionship."""
 
 
-class Dog(Pet):
-    """Canis familiaris"""
-
-
 class Cat(Pet):
     """Felis catus"""