set timezone/dst from lat/long using timezonefinder

Author: verhovsky

pyzipcode/update_timezones.py

@@ -0,0 +1,87 @@
+"""
+A script to update the timezone data in the zipcode CSV file
+============================================================
+
+Reads the zipcode CSV file and updates the timezone/dst fields using
+the lat/long coordinates.
+
+Requires pytz and timezonefinder
+
+Example usage::
+
+   # Assumes the file ./zipcode.csv exists and contains zipcode data
+   python update_timezones.py
+
+"""
+
+import csv
+import datetime
+import shutil
+import tempfile
+import sys
+from pathlib import Path
+
+import pytz
+from timezonefinder import TimezoneFinder
+
+try:
+    from settings import db_location, csv_location
+except ImportError:
+    from pyzipcode.settings import db_location, csv_location
+
+BEFORE_DST_DATE = datetime.datetime(2021, 2, 1)
+DST_DATE = datetime.datetime(2021, 4, 1)
+
+tf = TimezoneFinder()
+
+
+def coords_to_utcoffset_and_isdst(lng, lat):
+    timezone_name = tf.timezone_at(lng=lng, lat=lat)
+    timezone = pytz.timezone(timezone_name)
+    offset = timezone.utcoffset(BEFORE_DST_DATE).total_seconds() / 60 / 60
+    dst = timezone.dst(DST_DATE).total_seconds() / 60 / 60
+    return offset, dst, timezone_name
+
+
+def run_update():
+    """Run the import code."""
+    with open(csv_location, newline="", encoding="utf-8") as f:
+        reader = csv.reader(f)
+        header = next(reader)
+
+        new_rows = []
+        for i, row in enumerate(reader, start=1):
+            zip, city, state, lat, longt, timezone, dst = row
+            longt, lat = float(longt), float(lat)
+            timezone, dst = float(timezone), float(dst)
+
+            new_timezone, new_dst, tz_name = coords_to_utcoffset_and_isdst(longt, lat)
+            if timezone != new_timezone or dst != new_dst:
+                print(
+                    f"line {i: >5}: {zip}, {city: <26}, {state}, {lat}, {longt}\n"
+                    f"{timezone},{dst} -> {new_timezone},{new_dst} ({tz_name})\n",
+                    file=sys.stderr,
+                )
+
+            if new_timezone != int(new_timezone):
+                raise ValueError("USA has fractional-hour timezones now")
+            if new_dst not in [1, 0]:
+                raise ValueError("expected dst to be either +1 or 0")
+
+            new_timezone, new_dst = int(new_timezone), int(new_dst)
+            new_rows.append([zip, city, state, lat, longt, new_timezone, new_dst])
+
+    with tempfile.TemporaryDirectory() as tempdir:
+        out_filename = Path(tempdir) / "zipcode.csv"
+
+        with open(out_filename, "w", newline="", encoding="utf-8") as f:
+            writer = csv.writer(f, lineterminator="\n")
+            writer.writerow(header)
+            writer.writerows(new_rows)
+
+        Path(csv_location).unlink()
+        shutil.move(out_filename, csv_location)
+
+
+if __name__ == "__main__":
+    run_update()