Get the named timezone for a given location in python using native macOS CoreLocation APIs

tzname.py

"""Get named timezone for a location on macOS using CoreLocation

To use this script, you need to have pyobjc-core and pyobjc-framework-CoreLocation installed:

    pip install pyobjc-core pyobjc-framework-CoreLocation

This script uses CoreLocation to get the timezone for a given latitude and longitude
as well as the timezone offset for a given date.

It effectively does the same thing as python packages like [tzfpy](https://pypi.org/project/tzfpy/)
or [timezonefinder](https://pypi.org/project/timezonefinder/) but uses macOS native APIs.

"""

# /// script
# dependencies = [
#     "pyobjc-core",
#     "pyobjc-framework-CoreLocation"
# ]
# ///

import datetime

import objc
from CoreLocation import CLGeocoder, CLLocation
from Foundation import NSDate, NSRunLoop, NSTimeZone

WAIT_FOR_COMPLETION = 0.01  # wait time for async completion in seconds
COMPLETION_TIMEOUT = 5.0  # timeout for async completion in seconds


def timezone_for_location(latitude: float, longitude: float) -> NSTimeZone:
    with objc.autorelease_pool():
        location = CLLocation.alloc().initWithLatitude_longitude_(latitude, longitude)
        geocoder = CLGeocoder.alloc().init()

        result = {"timezone": None, "error": None}
        completed = False

        def completion(placemarks, error):
            nonlocal completed
            if error:
                result["error"] = error.localizedDescription()
            else:
                placemark = placemarks[0] if placemarks else None
                if placemark and placemark.timeZone():
                    result["timezone"] = placemark.timeZone()
                else:
                    result["error"] = "Unable to determine timezone"
            completed = True

        geocoder.reverseGeocodeLocation_completionHandler_(location, completion)

        # reverseGeocodeLocation_completionHandler_ is async so run the event loop until completion
        # I usuall use threading.Event for this type of thing in pyobjc but the the thread blocked forever
        waiting = 0
        while not completed:
            NSRunLoop.currentRunLoop().runMode_beforeDate_(
                "NSDefaultRunLoopMode",
                NSDate.dateWithTimeIntervalSinceNow_(WAIT_FOR_COMPLETION),
            )
            waiting += WAIT_FOR_COMPLETION
            if waiting >= COMPLETION_TIMEOUT:
                raise TimeoutError(
                    f"Timeout waiting for completion of reverseGeocodeLocation_completionHandler_: {waiting} seconds"
                )

        if result["error"]:
            raise Exception(f"Error: {result['error']}")

        return result["timezone"]


if __name__ == "__main__":
    import argparse
    import time

    def parse_date(date_str):
        try:
            return datetime.datetime.strptime(date_str, "%Y-%m-%d %H:%M:%S")
        except ValueError:
            return datetime.datetime.strptime(date_str, "%Y-%m-%d")

    parser = argparse.ArgumentParser(description="Get timezone for a location")
    parser.add_argument("latitude", type=float, help="Latitude of location")
    parser.add_argument("longitude", type=float, help="Longitude of location")
    parser.add_argument(
        "--date",
        type=lambda d: parse_date(d),
        default=datetime.datetime.now(),
        help="Date/time for timezone offset in format 'YYYY-MM-DD HH:MM:SS' or 'YYYY-MM-DD'",
    )
    args = parser.parse_args()

    try:
        start_t = time.time_ns()
        timezone = timezone_for_location(args.latitude, args.longitude)
        offset = timezone.secondsFromGMTForDate_(
            args.date
        )  # takes an NSDate but pybojc will convert
        end_t = time.time_ns()
        print(
            f"Timezone: {timezone.name()}, offset: {offset}, took: {(end_t - start_t) / 1e6:.2f} ms"
        )
    except Exception as e:
        print(f"Error: {e}")

Very nice, thank you