Strict typing

main.py

@@ -3,8 +3,8 @@ Present observational weather data to Prometheus
 """
 
 import json
-import time
 import os
+from typing import Dict, List, TypedDict
 
 import requests
 from flask import Flask, Response
@@ -12,7 +12,21 @@ from flask import Flask, Response
 app = Flask(__name__)
 
 
-def fetch_weather_data(location: int, apikey: str) -> dict:
+class PromData(TypedDict):
+    """
+    Describes the data being returned to Prometheus
+
+    Args:
+        TypedDict ([type]): data to return to Prometheus
+    """
+
+    key: str
+    labels: Dict[str, str]
+    type: str
+    value: float
+
+
+def fetch_weather_data(location: int, apikey: str) -> Dict[str, Dict[str, float]]:
     """
     Fetch current data from the Met Office for the provided postcode
     """
@@ -24,20 +38,26 @@ def fetch_weather_data(location: int, apikey: str) -> dict:
         f'aqi=yes'
     )
 
-    return json.loads(obs_data.content)
+    return dict(json.loads(obs_data.content))
 
 
 @app.route('/metrics')
-def metrics():
+def metrics() -> Response:
     """
     Output Prometheus-style metrics
     """
     apikey = os.environ.get('WEATHER_APIKEY')
     location = os.environ.get('WEATHER_LOCATION')
 
-    latest_data = fetch_weather_data(location, apikey)['current']
+    if not location:
+        return Response(
+            f'There was a problem finding the weather for location: "{location}"',
+            status=500,
+        )
 
-    ret_data = [
+    latest_data = fetch_weather_data(int(location), str(apikey))['current']
+
+    ret_data: List[PromData] = [
         {
             'key': 'sensor_weather_outdoor_temperature_celsius',
             'labels': {
@@ -120,12 +140,12 @@ def metrics():
         },
     ]
 
-    ret_strs = list()
+    ret_strs = []
     for item in ret_data:
         ret_strs.append(f'# HELP {item["key"]} Weather metric')
         ret_strs.append(f'# TYPE {item["key"]} {item["type"]}')
         ret_strs.append(
-            item["key"]
+            str(item["key"])
             + '{'
             + " ".join([f'{key}="{val}"' for key, val in item["labels"].items()])
             + '} '