observer_pattern.py

import random
from abc import ABC, abstractmethod



class Observer(ABC):

    @abstractmethod
    def update(self, data: "Observable"):
        raise NotImplementedError


class Observable(ABC):

    @abstractmethod
    def add_observer(self, observer: Observer):
        raise NotImplementedError

    @abstractmethod
    def remove_observer(self, observer: Observer):
        raise NotImplementedError

    @abstractmethod
    def notify_observers(self):
        raise NotImplementedError


class WeatherData(Observable):

    def __init__(self):
        self._temperature = None
        self._humidity = None
        self.observers: list[Observer] = []

    def add_observer(self, observer: Observer):
        self.observers.append(observer)

    def remove_observer(self, observer: Observer):
        index = self.observers.index(observer)
        if index >= 0:
            self.observers.remove(observer)

    def notify_observers(self):
        print("Len",  len(self.observers))
        for observer in self.observers:
            observer.update(self)

    def set_weather_data(self):
        self._temperature = random.randint(-10, 30)
        self._humidity = random.randint(0, 100)
        self.notify_observers()

    @property
    def temperature(self):
        return self._temperature

    @property
    def humidity(self):
        return self._humidity


class DisplayElement(ABC):

    def display(self):
        raise NotImplementedError

class CurrentConditionDisplay(Observer, DisplayElement):
    def __init__(self):
        self._temperature = None
        self._humidity = None

    def update(self, data):
        if isinstance(data, WeatherData):
            if data.temperature > 0 and data.humidity > 0:
                self._temperature = data.temperature
                self._humidity = data.humidity
                self.display()

    def display(self):
        print(f"Current conditions: {self._temperature} temp degrees, humidity: {self._humidity} %")


weather_data = WeatherData()
current_condition_display = CurrentConditionDisplay()

weather_data.add_observer(current_condition_display)

weather_data.set_weather_data()
# weather_data.remove_observer(current_condition_display)

weather_data.set_weather_data()