invite_customers.py

import json
from math import radians, cos, sin, acos, sqrt, pi


DUBLIN_HQ = {"lat" : 53.3381985, 
             "lon" : -6.2592576}
EARTH_RADIUS = 6371 #km
FILTER_RADIUS = 100 #km

#two points, expected result, floating error epsilon
DISTANCES = [
([{"lat" : 0,"lon" : 0}, {"lat" : 0,"lon" : 180}] , pi * EARTH_RADIUS , 0.0001)
#...
]

def read_customers(fname):
    result = []
    try:
        with open(fname) as f:
            content = f.readlines()
            for i,line in enumerate(content):
                result.append(json.loads(line))
    except IOError:
        print 'cannot open', fname
    except:
        print 'generic error'

    return result


def read_customers_test():
    if len(read_customers('customers.json')) == 0:
        return False
    if len(read_customers('custmers.json')) != 0:
        return False
    if len(read_customers(1)) != 0:
        return False
    print ()
    return True


def haversine_distance(point_a,point_b):
    #convert to radians
    lon1, lat1, lon2, lat2 = map(radians, [point_a['lon'], point_a['lat'], point_b['lon'], point_b['lat']])

    delta_lon = lon2 - lon1

    a = sin(lat1)*sin(lat2) + cos(lat1) * cos(lat2)*cos(delta_lon)
    return acos(a) * EARTH_RADIUS  #km

def haversine_distance_test():
    for i,tup in enumerate(DISTANCES):
        if haversine_distance(tup[0][0],tup[0][1]) - tup[1] > tup[2]:
            print "not equal"
            return False
    return True


def is_near(customer):
    c_point = {}
    c_point['lat'] = float(customer['latitude'])
    c_point['lon'] = float(customer['longitude'])
    if haversine_distance(c_point, DUBLIN_HQ) < FILTER_RADIUS:
        return True
    return False


def filter_customers(customers,func):
    return filter(lambda s: func(s), customers)

def invite():
    customers = read_customers('customers.json')
    #filter
    near_customers = filter_customers(customers, is_near)
    #sort by id
    near_customers.sort(key=lambda x: x['user_id'], reverse=False)

    for c in near_customers:
        print c['name'],",",c['user_id']

if __name__ == "__main__":
    #perform some tests here
    print "TESTS:"
    if read_customers_test() and haversine_distance_test():
        print "All tests passed\n"
    else:
        print "Tests failed"

    #run
    invite()