Update app/price_fetcher.py

app/price_fetcher.py

@@ -10,7 +10,12 @@ Features:
 """
 import asyncio
 import logging
-from typing import Callable, TypedDict, Awaitable
+# ====================================================================
+#                       FIX APPLIED HERE (1 of 2)
+# ====================================================================
+# Import Union for Python 3.9 compatibility, and other necessary types.
+from typing import Callable, TypedDict, Awaitable, Union
+# ====================================================================
 
 import httpx
 
@@ -46,7 +51,7 @@ class PriceFetcher:
         """
         self.client = client
         self.coins = coins
-        self._prices: dict[str, float | str] = {coin: "--" for coin in coins}
+        self._prices: dict[str, Union[float, str]] = {coin: "--" for coin in coins}
         self._lock = asyncio.Lock()  # Lock to prevent race conditions on the cache
         self.sources: list[PriceSource] = self._configure_sources()
 
@@ -92,8 +97,13 @@ class PriceFetcher:
         except (KeyError, TypeError, ValueError) as e:
             logging.error("❌ [CoinCap] Failed to parse response: %s", e)
             return {}
-
-    def get_current_prices(self) -> dict[str, float | str]:
+    
+    # ====================================================================
+    #                       FIX APPLIED HERE (2 of 2)
+    # ====================================================================
+    # Changed the type hint from `float | str` to `Union[float, str]`.
+    def get_current_prices(self) -> dict[str, Union[float, str]]:
+    # ====================================================================
         """Returns a copy of the current price cache. Thread-safe read."""
         return self._prices.copy()
 
@@ -132,44 +142,4 @@ class PriceFetcher:
             # Brief pause before trying the next API source
             await asyncio.sleep(1)
 
-        logging.error("❌ All price APIs failed. Retaining stale prices.")
-
-
-async def run_price_updates_periodically(fetcher: PriceFetcher, interval_seconds: int):
-    """A background task runner to keep prices updated."""
-    logging.info("🚀 Starting periodic price updates...")
-    while True:
-        await fetcher.update_prices_async()
-        await asyncio.sleep(interval_seconds)
-
-
-# --- Example Usage ---
-if __name__ == "__main__":
-    async def main():
-        """Demonstrates how to use the PriceFetcher."""
-        target_coins = ["bitcoin", "ethereum", "dogecoin"]
-        
-        async with httpx.AsyncClient() as client:
-            price_fetcher = PriceFetcher(client, coins=target_coins)
-
-            # Run the price updates in the background
-            update_task = asyncio.create_task(
-                run_price_updates_periodically(price_fetcher, interval_seconds=10)
-            )
-
-            # In a real app, the server would be running. Here, we just print prices.
-            for i in range(5):
-                await asyncio.sleep(11)
-                current_prices = price_fetcher.get_current_prices()
-                print(f"--- Main App Reading Cache ({i+1}/5) ---")
-                for coin, price in current_prices.items():
-                    print(f"  {coin.capitalize()}: ${price}")
-            
-            # Cleanly shut down the background task
-            update_task.cancel()
-            try:
-                await update_task
-            except asyncio.CancelledError:
-                logging.info("Shutdown complete.")
-
-    asyncio.run(main())
+        logging.error("❌ All price APIs failed. Retaining stale prices.")