add ticker validation

app.ipynb

@@ -33,7 +33,7 @@
        "        "
       ],
       "text/plain": [
-       "<IPython.lib.display.IFrame at 0x10f60e840>"
+       "<IPython.lib.display.IFrame at 0x119e2b890>"
       ]
      },
      "metadata": {},

src/dash_app.py

@@ -7,7 +7,12 @@ from src.style_elements import (
     setup_interval_buttons,
     setup_ticker_selection,
 )
-from src.utils import adjust_date_range, date_to_idx_range, get_date_range
+from src.utils import (
+    adjust_date_range,
+    date_to_idx_range,
+    get_date_range,
+    normalize_ticker_symbol,
+)
 
 
 class NormalizedAssetPricesApp:
@@ -96,6 +101,7 @@ class NormalizedAssetPricesApp:
                 Output("ticker-selection", "options"),
                 Output("ticker-selection", "value"),
                 Output("ticker-input", "value"),
+                Output("ticker-input", "placeholder"),
             ],
             [Input("ticker-input", "n_submit"), Input("ticker-selection", "value")],
             [State("ticker-input", "value"), State("ticker-selection", "value")],
@@ -103,16 +109,23 @@ class NormalizedAssetPricesApp:
         )
         def update_tickers(n_submit, selected_tickers, input_ticker, current_tickers):
             triggered_id = ctx.triggered_id
+            tickers = current_tickers if current_tickers else []
+            options = [{"label": t, "value": t} for t in tickers]
+
             if triggered_id == "ticker-input" and input_ticker and input_ticker.strip():
-                ticker = input_ticker.strip().upper()
-                tickers = current_tickers if current_tickers else []
-                if ticker not in tickers:
+                ticker = normalize_ticker_symbol(input_ticker)
+                if ticker in tickers:
+                    return options, tickers, "", f"⚠️ `{ticker}` already added"
+                elif not self.prices.is_valid_ticker(ticker):
+                    return options, tickers, "", f"❌ `{ticker}` is not valid"
+                else:
                     tickers = tickers + [ticker]
+                    options = [{"label": t, "value": t} for t in tickers]
+                    return options, tickers, "", f"✅ `{ticker}` added"
+            else:
+                tickers = selected_tickers if selected_tickers else []
                 options = [{"label": t, "value": t} for t in tickers]
-                return options, tickers, ""
-            tickers = selected_tickers if selected_tickers else []
-            options = [{"label": t, "value": t} for t in tickers]
-            return options, tickers, input_ticker or ""
+                return options, tickers, input_ticker or "", "Enter ticker symbol..."
 
         @self.app.callback(
             Output("plotly-normalized-asset-prices", "figure"),

src/prices.py

@@ -68,8 +68,8 @@ class Prices:
             df.drop(ticker, axis=1, inplace=True)
 
     def add_ticker(self, ticker):
-        self.tickers.append(ticker)
         ticker_df = self.get_historical_prices(ticker)
+        self.tickers.append(ticker)
         self.prices_raw[ticker] = ticker_df
         self.prices_normalized[ticker] = ticker_df / ticker_df.iloc[0]
         self.percentage_changes[ticker] = (
@@ -81,3 +81,10 @@ class Prices:
             .rolling(window=PRICES_ROLLING_WINDOW, min_periods=PRICES_ROLLING_MIN_PERIOD)
             .sum()
         )
+
+    def is_valid_ticker(self, ticker):
+        try:
+            data = yf.download(ticker, period="5d", progress=False, auto_adjust=False)
+            return data is not None and not data.empty
+        except Exception:
+            return False

src/utils.py

@@ -1,3 +1,4 @@
+import re
 from datetime import timedelta
 
 import numpy as np
@@ -5,7 +6,13 @@ import pandas as pd
 from dateutil import parser  # type: ignore
 
 
+def normalize_ticker_symbol(ticker_input):
+    """Remove all non-alphanumeric characters from ticker input, return uppercase."""
+    return re.sub(r"[^A-Z0-9]", "", ticker_input.upper())
+
+
 def get_available_tickers():
+    """This list is too limited, I opted for any input + validation in the app."""
     nasdaq_url = "https://www.nasdaqtrader.com/dynamic/SymDir/nasdaqlisted.txt"
     nyse_url = "https://www.nasdaqtrader.com/dynamic/SymDir/otherlisted.txt"
     nasdaq_tickers = pd.read_csv(nasdaq_url, sep="|")["Symbol"].dropna().tolist()[:-1]