Validate user input and convert to constrained types

Author: ike-agu

prep_exercise/8_enums.py

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+from dataclasses import dataclass
+from enum import Enum
+from typing import List, Dict
+import sys
+
+class OperatingSystem(Enum):
+    MACOS = "macOS"
+    ARCH = "Arch Linux"
+    UBUNTU = "Ubuntu"
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    age: int
+    preferred_operating_system: OperatingSystem
+
+
+@dataclass(frozen=True)
+class Laptop:
+    id: int
+    manufacturer: str
+    model: str
+    screen_size_in_inches: float
+    operating_system: OperatingSystem
+
+# =====define parse age======
+def parse_age(raw: str) -> int:
+    try:
+        age= int(raw)
+    except ValueError:
+        print("Error: age must be asn integer.", file=sys.stderr)
+        sys.exit(1)
+
+    if age <= 0:
+        print("Error: age must be a positive integer.", file=sys.stderr)
+        sys.exit(1)
+
+    return age
+
+# =====define parse operating system======
+def parse_operating_system(raw: str) -> OperatingSystem:
+    normalized = raw.strip().lower()
+
+    aliases = {
+        "macos": OperatingSystem.MACOS,
+        "mac": OperatingSystem.MACOS,
+        "arch": OperatingSystem.ARCH,
+        "arch linux": OperatingSystem.ARCH,
+        "ubuntu": OperatingSystem.UBUNTU,
+    }
+
+    if normalized not in aliases:
+        valid = ", ".join(sorted(aliases.keys()))
+        print(f"Error: invalid operating system. Try one of: {valid}", file=sys.stderr)
+        sys.exit(1)
+
+    return aliases[normalized]
+
+
+# =======count laptops by os============
+def count_laptops_by_os(laptops: List[Laptop]) -> Dict[OperatingSystem, int]:
+    counts: Dict[OperatingSystem, int] = {os: 0 for os in OperatingSystem}
+    for laptop in laptops:
+        counts[laptop.operating_system] +=1
+    return counts
+
+
+# ======define main ================
+def main() -> None:
+    laptops = [
+    Laptop(id=1, manufacturer="Dell", model="XPS", screen_size_in_inches=13.0, operating_system=OperatingSystem.ARCH),
+    Laptop(id=2, manufacturer="Dell", model="XPS", screen_size_in_inches=15.0, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=3, manufacturer="Dell", model="XPS", screen_size_in_inches=15.0, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=4, manufacturer="Apple", model="macBook", screen_size_in_inches=13.0, operating_system=OperatingSystem.MACOS),
+]
+
+    name = input("Enter your name: ").strip()
+    if not name:
+        print("Error: name cannot be empty.", file=sys.stderr)
+        sys.exit(1)
+
+    age = parse_age(input("Enter your age: "))
+    preferred_os = parse_operating_system(input("preferred OS(Ubuntu / Arch / macOS): "))
+
+    person = Person(name=name, age=age, preferred_operating_system=preferred_os)
+
+    counts = count_laptops_by_os(laptops)
+    preferred_count = counts[person.preferred_operating_system]
+
+    print(f"\nHi {person.name} (age {person.age})")
+    print(f"Laptops available with {person.preferred_operating_system.value}: {preferred_count}")
+
+    # Find the OS with maximum availability
+    best_os = max(counts, key=lambda os:counts[os])
+    best_count = counts[best_os]
+
+    if best_os != person.preferred_operating_system and best_count > preferred_count:
+        print(
+            f"If you are willing to accept {best_os.value} instead,"
+            f"You're more likely to get a laptop. {best_count} available)."
+        )
+
+if __name__ == "__main__":
+    main()