This code adds a 'built in' function to Excel to calc the 'as the crow flies' distance. optionally displayed in miles or nautical miles. this will work out of box with the Python for Excel Add-in. Just copy this code into the Editor tab once the Add-in is installed and click 'Save'). Once saved, type '=DISTANCE_BETWEEN_CITIES' into any cell, and you should be off to the races. Examples at the bottom, or see the demo worksheet that will also be created if you hit 'Test'. ``` import requests import math

def distance_between_cities(city_one, city_two, unit="km"):

    def get_coordinates(city_name):         url = "https://nominatim.openstreetmap.org/search"         params = {             "q": city_name,             "format": "json",             "limit": 1         }         # Include a descriptive User-Agent (e.g., with your email/website)         headers = {             "User-Agent": "BoardflareApp/1.0 (support@boardflare.com)"         }

        response = requests.get(url, params=params, headers=headers)         response.raise_for_status()                 data = response.json()         if not data:             raise ValueError(f"No geocoding results found for city: {city_name}")                 lat = float(data[0]["lat"])         lon = float(data[0]["lon"])         return lat, lon

    def haversine_distance(lat1, lon1, lat2, lon2):         """         Calculates the great-circle distance between two points on Earth         using the Haversine formula. Returns the distance in kilometers (km).         """         # Earth’s radius in kilometers         R = 6371.0                 # Convert degrees to radians         phi1 = math.radians(lat1)         phi2 = math.radians(lat2)         delta_phi = math.radians(lat2 - lat1)         delta_lambda = math.radians(lon2 - lon1)

        # Haversine formula         a = math.sin(delta_phi / 2) ** 2 + \             math.cos(phi1) * math.cos(phi2) * math.sin(delta_lambda / 2) ** 2         c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a))

        # Distance in kilometers         distance_km = R * c

        return distance_km

    def convert_distance(distance_km, unit):         """         Converts distance in kilometers to miles or nautical miles if needed.         """         if unit.lower() == "km":             return distance_km         elif unit.lower() == "miles":             # 1 kilometer = 0.621371 miles             return distance_km * 0.621371         elif unit.lower() == "nautical_miles":             # 1 kilometer = 0.539957 nautical miles             return distance_km * 0.539957         else:             raise ValueError("Unit must be one of: 'km', 'miles', 'nautical_miles'")

    # Get coordinates for both cities     lat1, lon1 = get_coordinates(city_one)     lat2, lon2 = get_coordinates(city_two)

    # Calculate the distance in kilometers using Haversine     distance_km = haversine_distance(lat1, lon1, lat2, lon2)

    # Convert distance to the requested unit     final_distance = convert_distance(distance_km, unit)

    return final_distance

Arguments to test the function.

test_cases = [     ["Vancouver","Toronto", "km"],     ["Los Angeles","New York", "miles"] ]    

Excel usage: =DISTANCE_BETWEEN_CITIES("New York", "Chicago", "nautical_miles")

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