Function to compute distance in Miles or Kilometers between two latitude, longitude points on Earth using the Haversine formula

Distance.py

'''Haversine formula - Shortest distance between two points on a sphere

Steps:
    1) Convert lat,long for two points from degrees to radians --> divide by 180/pi == 57.29577951
    2) Earth radius in miles -> 3958.8, Km -> 6371
    3) Formula
        hav(lat2 - lat1) + cos(lat1)*cos(lat2)*hav(long2-long1)
        hav(theta) = sin^2(theta/2) = (1 - cos(theta)) / 2
        Let h = hav(theta)
        d = radius * archav(h) = 2 * radius * arcsin(sqrt(h))
Refs:
    https://en.wikipedia.org/wiki/Haversine_formula "the haversine formula and law of cosines cannot be guaranteed correct to better than 0.5%."
'''
from math import radians, cos, sin, asin, sqrt

def distance(coords1,coords2,unit='Miles'):
    '''Function to find the distance between two latitude, longitude points on earth

    Args:
        coords1 (tuple): Tuple containing the latitude/longitude of point 1
        coords2 (tuple): Tuple containing the latitude/longitude of point 2
        unit (string): Value to switch unit of measure, default is Miles other option is Kilometers
    
    Returns:
        distance (float): Distance calculated between two points on a sphere using the haversine formula
    '''
    lat1 = radians(coords1[0])
    long1 = radians(coords1[1])
    lat2 = radians(coords2[0])
    long2 = radians(coords2[1])
    
    delta_long = long2 - long1
    delta_lat = lat2 - lat1

    #Compute haversine of two points
    a = sin(delta_lat / 2)**2 + cos(lat1) * cos(lat2) * sin(delta_long/2)**2
    #Compute distance by completing the formula
    c = 2 * asin(sqrt(a))
    #Select radius value for earth based on unit
    r = 3958.8
    if unit == 'Kilometers':
        r = 6371
    return c * r


if __name__ == "__main__":
    #Philly
    point1 = (39.952031,-75.166068)
    #NYC
    point2 = (40.709422,-74.006358)
    print(distance(point1,point2),'Miles')
    print(distance(point1,point2,unit='Kilometers'),'Kilometers')