Drill 21: Inputs and outputs — Project: course tracker

import json
from dataclasses import dataclass, field

@dataclass
class Tracker:
    learner: str
    completed: set[str] = field(default_factory=set)

    def complete(self, lesson: str) -> None:
        self.completed.add(lesson)

    def percent(self, total: int) -> float:
        return len(self.completed) / total * 100 if total else 0.0

    def to_json(self) -> str:
        return json.dumps(
            {"learner": self.learner, "completed": sorted(self.completed)}
        )

tracker = Tracker("Ada")
tracker.complete("getting-started")
tracker.complete("control-flow")
print(f"{tracker.percent(12):.0f}% complete")
print(tracker.to_json())