Merge pull request #8 from dancergraham/feature/observer

feature: Complete the weather station code

Author: dancergraham

chapter02_observer/weather.py

@@ -1,26 +1,29 @@
 class Subject:
-    def register_observer():
+    def register_observer(self, observer):
         raise NotImplementedError
 
-    def remove_observer():
+    def remove_observer(self, observer):
         raise NotImplementedError
 
-    def notify_observers():
+    def notify_observers(self):
         raise NotImplementedError
 
 
 class Observer:
-    def update():
+    def update(self, temp, humidity, pressure):
         raise NotImplementedError
 
 
 class DisplayElement:
-    def display():
+    def display(self):
         raise NotImplementedError
 
 
 class WeatherData(Subject):
     def __init__(self):
+        self._temperature = None
+        self._humidity = None
+        self._pressure = None
         self._observers = []
 
     def register_observer(self, observer: Observer):
@@ -49,23 +52,80 @@ def __init__(self, weather_data):
 
     def display(self):
         print(
-            f"Current conditions: {self._temperature:.1f}F degrees and {self._humidity:.1f}% humidity"
+            f"Current conditions: "
+            f"{self._temperature:.1f}F degrees and "
+            f"{self._humidity:.1f}% humidity"
         )
 
-    def update(self, temperature: float, humidity: float, pressure: float):
-        self._temperature = temperature
+    def update(self, temp: float, humidity: float, pressure: float):
+        self._temperature = temp
         self._humidity = humidity
         self.display()
 
 
+class StatisticsDisplay(DisplayElement, Observer):
+
+    def __init__(self, weather_data):
+        self._max_temp = 0.
+        self._min_temp = 200.
+        self._temp_sum = 0.
+        self._num_readings = 0
+        self._weather_data = None
+        self._weather_data = weather_data
+        weather_data.register_observer(self)
+
+    def update(self, temp, humidity, pressure):
+        self._temp_sum += temp
+        self._num_readings += 1
+        self._max_temp = max(temp, self._max_temp)
+        self._min_temp = min(temp, self._min_temp)
+        self.display()
+
+    def display(self):
+        print(f"Avg/Max/Min temperature = "
+              f"{self._temp_sum / self._num_readings}"
+              f"/{self._max_temp}"
+              f"/{self._min_temp}"
+              )
+
+
+class ForecastDisplay(DisplayElement, Observer):
+
+    def __init__(self, weather_data):
+        self._current_pressure = 29.92
+        self._last_pressure = None
+        self._weather_data = weather_data
+        weather_data.register_observer(self)
+
+    def update(self, temp, humidity, pressure):
+        self._last_pressure = self._current_pressure
+        self._current_pressure = pressure
+        self.display()
+
+    def display(self):
+        print("Forecast: ", end="")
+        if self._current_pressure > self._last_pressure:
+            print("Improving weather on the way!")
+        elif self._current_pressure == self._last_pressure:
+            print("More of the same")
+        elif self._current_pressure < self._last_pressure:
+            print("Watch out for cooler, rainy weather")
+
+
 def weather_station():
     weather_data = WeatherData()
+
     current_display = CurrentConditionsDisplay(weather_data)
-    #   statistics_display = StatisticsDisplay(weather_data)
+    statistics_display = StatisticsDisplay(weather_data)
+    forecast_display = ForecastDisplay(weather_data)
+
     weather_data.set_measurements(80, 65, 30.4)
     weather_data.set_measurements(82, 70, 29.2)
     weather_data.set_measurements(78, 90, 29.2)
 
+    weather_data.remove_observer(forecast_display)
+    weather_data.set_measurements(62, 90, 28.1)
+
 
 if __name__ == "__main__":
     weather_station()