fix: move expensive TimezoneFinder call out of top level.

src/pudl/transform/eia.py

@@ -45,10 +45,6 @@
 logger = pudl.logging_helpers.get_logger(__name__)
 
 
-TZ_FINDER = timezonefinder.TimezoneFinder()
-"""A global TimezoneFinder to cache geographies in memory for faster access."""
-
-
 class EiaEntity(StrEnum):
     """Enum for the different types of EIA entities."""
 
@@ -58,7 +54,7 @@ class EiaEntity(StrEnum):
     GENERATORS = auto()
 
 
-def find_timezone(*, lng=None, lat=None, state=None, strict=True):
+def find_timezone(*, lng=None, lat=None, state=None, strict=True, tz_finder=None):
     """Find the timezone associated with the a specified input location.
 
     Note that this function requires named arguments. The names are lng, lat,
@@ -84,10 +80,10 @@ def find_timezone(*, lng=None, lat=None, state=None, strict=True):
         Update docstring.
     """
     try:
-        tz = TZ_FINDER.timezone_at(lng=lng, lat=lat)
+        tz = tz_finder.timezone_at(lng=lng, lat=lat)
         if tz is None:  # Try harder
             # Could change the search radius as well
-            tz = TZ_FINDER.closest_timezone_at(lng=lng, lat=lat)
+            tz = tz_finder.closest_timezone_at(lng=lng, lat=lat)
     # For some reason w/ Python 3.6 we get a ValueError here, but with
     # Python 3.7 we get an OverflowError...
     except (OverflowError, ValueError) as err:
@@ -312,9 +308,16 @@ def _add_timezone(plants_entity: pd.DataFrame) -> pd.DataFrame:
         A DataFrame containing the same table, with a "timezone" column added.
         Timezone may be missing if lat / lon is missing or invalid.
     """
+    # Takes 300ms. Used to be at module level so we wouldn't have to initialize every time, but that makes import time slow.
+    tz_finder = timezonefinder.TimezoneFinder()
+
     plants_entity["timezone"] = plants_entity.apply(
         lambda row: find_timezone(
-            lng=row["longitude"], lat=row["latitude"], state=row["state"], strict=False
+            lng=row["longitude"],
+            lat=row["latitude"],
+            state=row["state"],
+            strict=False,
+            tz_finder=tz_finder,
         ),
         axis=1,
     )