Catalog: sort by (price, region name, zone name). (skypilot-org#1492)

Author: concretevitamin

sky/clouds/service_catalog/common.py

@@ -330,7 +330,10 @@ def get_region_zones(df: pd.DataFrame,
                      use_spot: bool) -> List[cloud_lib.Region]:
     """Returns a list of regions/zones from a dataframe."""
     price_str = 'SpotPrice' if use_spot else 'Price'
-    df = df.dropna(subset=[price_str]).sort_values(price_str)
+    sort_keys = [price_str, 'Region']
+    if 'AvailabilityZone' in df.columns:
+        sort_keys.append('AvailabilityZone')
+    df = df.dropna(subset=[price_str]).sort_values(sort_keys)
     regions = [cloud_lib.Region(region) for region in df['Region'].unique()]
     if 'AvailabilityZone' in df.columns:
         zones_in_region = df.groupby('Region')['AvailabilityZone'].apply(