separate callbacks for updating the info fields

main.py

@@ -19,13 +19,27 @@ from src.data import load_from_disk, load_from_thredds
 from src.layout import create_layout
 from src.thredds import get_datasets
 
-appconfig = DotDict.from_toml_file("./config/env.toml")
+# BEGIN state structures
+appconfig: DotDict = DotDict.from_toml_file("./config/env.toml")
 appconfig.VERSION = get_latest_semantic_version_tag() or appconfig.VERSION
-varconfig = pd.read_csv("./config/parms_units.csv", sep=";")
+
+varconfig: pd.DataFrame = pd.read_csv("./config/parms_units.csv", sep=";")
 varconfig = varconfig.set_index("VNAME")
-airportsconfig = pd.read_csv("./config/CARIBIC2_Airports.csv", sep=";")
+
+airportsconfig: pd.DataFrame = pd.read_csv("./config/CARIBIC2_Airports.csv", sep=";")
 airportsconfig = airportsconfig.set_index("IATA")
 
+# using separate variable declaration here to have a type annotation:
+data: pd.DataFrame = pd.DataFrame()
+ap_info: dict[int, str] = {}
+data, ap_info = (
+    load_from_thredds(get_datasets(appconfig), appconfig, airportsconfig, True)  # type: ignore
+    if appconfig.USE_THREDDS
+    else load_from_disk(Path("./testdata").glob("MS_*.nc"), appconfig, airportsconfig, True)  # type: ignore
+)
+log.debug(f"Data loaded. Used THREDDS: {appconfig.USE_THREDDS}")
+# END state structures
+
 # fmt: off
 app = Dash(
     appconfig.TITLE,
@@ -38,25 +52,32 @@ app.title = appconfig.TITLE
 app.css.config.serve_locally = True
 app.scripts.config.serve_locally = True
 
-data, ap_info = (
-    load_from_thredds(get_datasets(appconfig), appconfig, airportsconfig, True)  # type: ignore
-    if appconfig.USE_THREDDS
-    else load_from_disk(Path("./testdata").glob("MS_*.nc"), appconfig, airportsconfig, True)  # type: ignore
-)
-log.debug(f"Data loaded. Used THREDDS: {appconfig.USE_THREDDS}")
-# log.debug(f"Data size: {data.info()}")
-
 app.layout = create_layout(data, appconfig)
 server = app.server  # for deployment via gunicorn / WSGI server
 
 
+@app.callback(Output("var-info", "children"), Input("variable-dropdown", "value"))
+def set_var_info(selected_variable: str) -> str:
+    return varconfig.loc[selected_variable, :].Long_Name
+
+
+@app.callback(Output("second-var-info", "children"), Input("second-variable-dropdown", "value"))
+def set_second_var_info(secondary_variable: str) -> str:
+    return (
+        varconfig.loc[secondary_variable, :].Long_Name
+        if secondary_variable in varconfig.index
+        else ""
+    )
+
+@app.callback(Output("flight-dep-dest", "children"), Input("flight-dropdown", "value"))
+def set_flight_dep_dest(selected_flight: int) -> str:
+    return ap_info.get(selected_flight, "?!")
+
+
 @app.callback(
     [
         Output("fig-map", "figure"),
         Output("fig-ts", "figure"),
-        Output("flight-dep-dest", "children"),
-        Output("var-info", "children"),
-        Output("second-var-info", "children"),
     ],
     [
         Input("flight-dropdown", "value"),
@@ -68,15 +89,9 @@ def update_plots(selected_flight: int, primary_variable: str, secondary_variable
     filtered_df = data[data["flight_number"] == selected_flight]
     valid_indices = filtered_df[primary_variable].notna()
     unit_primary = varconfig.loc[primary_variable, :].Unit
-    lname_primary = (varconfig.loc[primary_variable, :].Long_Name,)
     unit_secondary = (
         varconfig.loc[secondary_variable, :].Unit if secondary_variable in varconfig.index else "-"
     )
-    lname_secondary = (
-        varconfig.loc[secondary_variable, :].Long_Name
-        if secondary_variable in varconfig.index
-        else ""
-    )
 
     fig_map = go.Figure(
         go.Scattermap(
@@ -193,12 +208,13 @@ def update_plots(selected_flight: int, primary_variable: str, secondary_variable
     fig_ts.update_yaxes(title=f"{primary_variable} {unit_primary}")
     fig_ts.update_yaxes(title=f"{secondary_variable} {unit_secondary}", secondary_y=True)
 
+    set_var_info(primary_variable)
+    set_second_var_info(secondary_variable)
+    set_flight_dep_dest(selected_flight)
+
     return [
         fig_map,
         fig_ts,
-        ap_info[selected_flight],
-        lname_primary,
-        lname_secondary,
     ]