updade from Atlas repo

15-more-types/cafeteria.py

@@ -2,25 +2,25 @@ from typing import TypeVar, Generic
 
 
 class Beverage:
-    """Any beverage"""
+    """Any beverage."""
 
 
 class Juice(Beverage):
-    """Any fruit juice"""
+    """Any fruit juice."""
 
 
 class OrangeJuice(Juice):
-    """Delicious juice from Brazilian oranges"""
+    """Delicious juice from Brazilian oranges."""
 
 
-BeverageT = TypeVar('BeverageT', covariant=True)
+T_co = TypeVar('T_co', covariant=True)
 
 
-class BeverageDispenser(Generic[BeverageT]):
-    def __init__(self, beverage: BeverageT) -> None:
+class BeverageDispenser(Generic[T_co]):
+    def __init__(self, beverage: T_co) -> None:
         self.beverage = beverage
 
-    def dispense(self) -> BeverageT:
+    def dispense(self) -> T_co:
         return self.beverage
 
 
@@ -36,11 +36,11 @@ class Compostable(Biodegradable):
     """Compostable garbage."""
 
 
-GarbageT = TypeVar('GarbageT', contravariant=True)
+T_contra = TypeVar('T_contra', contravariant=True)
 
 
-class TrashCan(Generic[GarbageT]):
-    def put(self, trash) -> None:
+class TrashCan(Generic[T_contra]):
+    def put(self, trash: T_contra) -> None:
         """Store trash until dumped..."""
 
 
@@ -48,35 +48,48 @@ class Cafeteria:
     def __init__(
         self,
         dispenser: BeverageDispenser[Juice],
-        trash_can: TrashCan[Biodegradable]
+        trash_can: TrashCan[Biodegradable],
     ):
         """Initialize..."""
 
 
-beverage_dispenser = BeverageDispenser(Beverage())
-juice_dispenser = BeverageDispenser(Juice())
-orange_juice_dispenser = BeverageDispenser(OrangeJuice())
+################################################ exact types
 
-trash_can: TrashCan[Garbage] = TrashCan()
+juice_dispenser = BeverageDispenser(Juice())
 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)
+
+################################################ covariant dispenser
+
+orange_juice_dispenser = BeverageDispenser(OrangeJuice())
+
+arnold_hall = Cafeteria(orange_juice_dispenser, bio_can)
+
+
+################################################ non-covariant dispenser
+
+beverage_dispenser = BeverageDispenser(Beverage())
 
 ## Argument 1 to "Cafeteria" has
 ## incompatible type "BeverageDispenser[Beverage]"
 ##          expected "BeverageDispenser[Juice]"
-# arnold_hall = Cafeteria(beverage_dispenser, trash_can)
+# arnold_hall = Cafeteria(beverage_dispenser, bio_can)
 
 
-######################## contravariance on 2nd argument
+################################################ contravariant trash
+
+trash_can: TrashCan[Garbage] = TrashCan()
+
+arnold_hall = Cafeteria(juice_dispenser, trash_can)
+
+
+################################################ non-contravariant trash
+
+compost_can: TrashCan[Compostable] = TrashCan()
 
 ## 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/petbox/petbox.py

@@ -29,14 +29,6 @@ class Box(Generic[T]):
         return self.contents
 
 
-T_contra = TypeVar('T_contra', contravariant=True)
-
-
-class InBox(Generic[T_contra]):
-    def put(self, item: T) -> None:
-        self.contents = item
-
-
 T_co = TypeVar('T_co', covariant=True)
 
 
@@ -46,3 +38,11 @@ class OutBox(Generic[T_co]):
 
     def get(self) -> Any:
         return self.contents
+
+
+T_contra = TypeVar('T_contra', contravariant=True)
+
+
+class InBox(Generic[T_contra]):
+    def put(self, item: T) -> None:
+        self.contents = item