Weather App LLD2026-05-13

This low-level design keeps the internal dashboard focused on one clean contract:

• Target: The interface the client expects.
• WeatherAdaptee: A legacy or third-party service that returns data in a different format.
• Adapter: Converts Fahrenheit to Celsius and miles per hour to kilometers per hour.
• Client: Consumes the normalized weather data without knowing anything about the external service.

The adapter isolates all translation logic so the dashboard does not depend on the legacy API shape.

Full Implementation

from abc import ABC, abstractmethod


class Target(ABC):
    @abstractmethod
    def get_weather(self):
        pass


class WeatherAdaptee:
    def get_raw_weather(self):
        # Simulates a third-party API returning Fahrenheit and miles per hour.
        return 72.0, 18.0


class Adapter(Target):
    def __init__(self, adaptee: WeatherAdaptee):
        self.adaptee = adaptee

    def get_weather(self):
        raw_temp_f, raw_speed_mph = self.adaptee.get_raw_weather()
        temp_c = (raw_temp_f - 32) * 5 / 9
        speed_kmh = raw_speed_mph * 1.60934
        return temp_c, speed_kmh


class Client:
    def __init__(self, provider: Target):
        self.provider = provider

    def display_dashboard(self):
        temp_c, speed_kmh = self.provider.get_weather()

        print("=== Toledo Weather Dashboard ===")
        print(f"Temperature: {temp_c:.2f} C")
        print(f"Wind Speed: {speed_kmh:.2f} km/h")
        print("==============================")


if __name__ == '__main__':
    legacy_api = WeatherAdaptee()
    weather_adapter = Adapter(legacy_api)

    app = Client(weather_adapter)
    app.display_dashboard()