Get distance from two cities

async_get_distance.py

import asyncio
import math
from typing import Any, Final

import aiohttp

earth_radius: Final[str] = 6_371  # km
host: str = "https://nominatim.openstreetmap.org/"
endpoint: str = "/search"
global_parameters: dict[str, Any] = {
    "addressdetails": 1,
    "format": "jsonv2",
    "limit": 1,
}


async def get_coords_city(
    session: aiohttp.ClientSession,
    city: str,
    queue: asyncio.Queue,
) -> str:
    query_parameters = global_parameters | {"city": city}

    async with session.get(endpoint, params=query_parameters) as response:
        print(f"Making request for {city}")
        await queue.put(await response.json())


def haversine(
    coords_1: tuple[float, float],
    coords_2: tuple[float, float],
) -> float:
    lat1, lon1 = coords_1
    lat2, lon2 = coords_2

    lat1_rad = math.radians(lat1)
    lon1_rad = math.radians(lon1)
    lat2_rad = math.radians(lat2)
    lon2_rad = math.radians(lon2)

    dlat = lat2_rad - lat1_rad
    dlon = lon2_rad - lon1_rad

    a = (
        math.sin(dlat / 2) ** 2
        + math.cos(lat1_rad) * math.cos(lat2_rad) * math.sin(dlon / 2) ** 2
    )
    c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a))

    distance = earth_radius * c

    return distance


async def main() -> None:
    city_a = input("Enter first city: ")
    city_b = input("Enter second city: ")

    queue = asyncio.Queue()
    async with aiohttp.ClientSession(host) as session, asyncio.TaskGroup() as group:
        for city in [city_a, city_b]:
            group.create_task(get_coords_city(session, city, queue))

    coords = []
    while not queue.empty():
        city = await queue.get()
        first_city, *_ = city
        city_coords = (float(first_city["lat"]), float(first_city["lon"]))
        coords.append(city_coords)
        print(f"{first_city['address']['city']} is in {city_coords}")

    distance = haversine(*coords)

    print(f"Distance between {city_a} and {city_b} is {distance:.2f} km")


if __name__ == "__main__":
    asyncio.run(main())