Comparing Lat/Lon values from the Database in Python

Question

I have a python Program that compares a particular Lat/Lon against a set of lat/lon and displays the closest lat/lot.The code is as follows:

def distance(lat1, lon1, lat2, lon2):
    p = 0.017453292519943295#degree to radian
    a = 0.5 - cos((lat2-lat1)*p)/2 + cos(lat1*p)*cos(lat2*p) * (1-cos((lon2-lon1)*p)) / 2
    return 12742 * asin(sqrt(a)) #print data in kms


def closest(data, v):
    return min(data, key=lambda p: distance(v['lat'],v['lon'],p['lat'],p['lon']))

sdata = [{'lat': 37.82, 'lon': 86.142}, 
    {'lat': 38.88,  'lon': 87.251 }, 
    {'lat': 39.78, 'lon': 89.336},
    {'lat': 40.42, 'lon': 86.123}, 
    {'lat': 41.35,  'lon': 90.21 }, 
    {'lat': 39.66, 'lon': 87.11}]

lat = input("Latitude:")
lon = input("Longitude:")

cust = {'lat': lat, 'lon':lon}

print(closest(sdata,cust))

Result:

Input: Latitude:45
Longitude:85
Output:{'lat': 40.42, 'lon': 86.123}

This snippet works fine however I want to integrate the data from my database.So there's a list of lat and lon from my database as such:

(('25.2748603820801', '55.327449798584'), ('25.2712', '55.298'), ('25.277031', '55.275226'), ('25.251389', '55.332222'), ('25.275397', '55.328213'), ('25.275397', '55.328213'))

How to I integrate the above code so that I can run a loop on the the values from database and compare the values among themselves without the input ie it gives me 7 different answers hopefully

Answer 1

Iterate over the tuple and convert to the required format of an array of dicts format in the following way and use it as input to your method.

sdata = (('25.2748603820801', '55.327449798584'), ('25.2712', '55.298'), ('25.277031', '55.275226'), ('25.251389', '55.332222'), ('25.275397', '55.328213'), ('25.275397', '55.328213'))
b = [{'lat':l1, 'lon':l2} for l1,l2 in sdata]

i = 0
for cust in b:
    tempb = [{'lat':l1, 'lon':l2} for l1,l2 in sdata]
    tempb.pop(i)
    print(closest(tempb,cust))
    i += 1

 #value of b
 [{'lat': '25.2748603820801', 'lon': '55.327449798584'}, 
 {'lat': '25.2712', 'lon': '55.298'}, 
 {'lat': '25.277031', 'lon': '55.275226'}, 
 {'lat': '25.251389', 'lon': '55.332222'}, 
 {'lat': '25.275397', 'lon': '55.328213'}, 
 {'lat': '25.275397', 'lon': '55.328213'}]