refactor: avoid repeated index lookups

powersimdata/scenario/helpers.py

@@ -57,9 +57,13 @@ def calculate_bus_demand(bus, demand):
     """
     zone_demand = bus.groupby("zone_id").sum().Pd
     bus_zone_share = bus.apply(lambda x: x.Pd / zone_demand.loc[x.zone_id], axis=1)
-    bus_to_zone = pd.DataFrame(index=zone_demand.index, columns=bus.index)
+    bus_to_zone = np.zeros((len(zone_demand), len(bus)))
+    bus_idx_lookup = {b: i for i, b in enumerate(bus.index)}
+    zone_idx_lookup = {z: i for i, z in enumerate(zone_demand.index)}
     for b in bus.index:
-        bus_to_zone.loc[bus.loc[b, "zone_id"], b] = bus_zone_share.loc[b]
+        bus_idx = bus_idx_lookup[b]
+        zone_idx = zone_idx_lookup[bus.loc[b, "zone_id"]]
+        bus_to_zone[zone_idx, bus_idx] = bus_zone_share.loc[b]
     bus_demand = pd.DataFrame(
         np.dot(demand.to_numpy(), bus_to_zone), index=demand.index, columns=bus.index
     )