task: Complete step 7 prep exercises

Author: jakr-s

prep-exercises/type_guided_refactorings.py

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+# ------------------------
+# Q. Try changing the type annotation of Person.preferred_operating_system from str to List[str].
+
+# Run mypy on the code.
+
+# It tells us different places that our code is now wrong, because we’re passing values of the wrong type.
+
+# We probably also want to rename our field - lists are plural. Rename the field to preferred_operating_systems.
+
+# Run mypy again.
+
+# Fix all of the places that mypy tells you need changing. Make sure the program works as you’d expect.
+
+# ------------------------
+
+# A.
+
+from dataclasses import dataclass
+from typing import List
+
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    age: int
+    preferred_operating_systems: List[str]
+
+
+@dataclass(frozen=True)
+class Laptop:
+    id: int
+    manufacturer: str
+    model: str
+    screen_size_in_inches: float
+    operating_system: str
+
+
+def find_possible_laptops(laptops: List[Laptop], person: Person) -> List[Laptop]:
+    possible_laptops: List[Laptop] = []
+    for laptop in laptops:
+        for operating_system in person.preferred_operating_systems:
+
+            if laptop.operating_system == operating_system:
+                possible_laptops.append(laptop)
+    return possible_laptops
+
+
+people = [
+    Person(name="Imran", age=22, preferred_operating_systems=[
+           "Ubuntu", "Arch Linux"]),
+    Person(name="Eliza", age=34, preferred_operating_systems=[
+           "Arch Linux", "macOS"]),
+]
+
+laptops = [
+    Laptop(id=1, manufacturer="Dell", model="XPS",
+           screen_size_in_inches=13, operating_system="Arch Linux"),
+    Laptop(id=2, manufacturer="Dell", model="XPS",
+           screen_size_in_inches=15, operating_system="Ubuntu"),
+    Laptop(id=3, manufacturer="Dell", model="XPS",
+           screen_size_in_inches=15, operating_system="ubuntu"),
+    Laptop(id=4, manufacturer="Apple", model="macBook",
+           screen_size_in_inches=13, operating_system="macOS"),
+]
+
+for person in people:
+    possible_laptops = find_possible_laptops(laptops, person)
+    print(f"Possible laptops for {person.name}: {possible_laptops}")