Calculate the great circle distance between two points on the earth (specified in decimal degrees)

haversine.py

def haversine(site_one, site_2):
    """
    Calculate the great circle distance between two points 
    on the earth (specified in decimal degrees)
    """
    lat1 , lon1 = site_one
    lat2 , lon2 = site_2
    # convert decimal degrees to radians 
    lon1, lat1, lon2, lat2 = map(radians, [lon1, lat1, lon2, lat2])
    distance = acos(sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(lon2-lon1))*6371
    distance = distance * 1000
    return distance

google = 37.422045, -122.084347
tower = 48.8582, 2.294407
opera = -33.856553, 151.214696
sf = 37.77493, -122.419416
print haversine(google,tower)