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The first part of my code is calculating the distance between two locations on Earth. The second part of my code is returning a list containing all of the cities stored in the database that are in the United States. The database is saved in a file named "city_data.db" containing a table named "cities" with columns ("country_code", "city_name", "region", "population", "latitude", "longitude"). Note that the country code for the United States is "us".

The third part of my code is returning a list containing all of the cities stored in the database that are in the United States sorted by their great circle distance from the city of Buffalo. Use (42.8864, -78.8784) for the latitude/longitude of Buffalo

I am getting error on input : findDistance() takes 0 positional arguments but 1 was given. What am I doing wrong?

import sqlite3

import math

conn = sqlite3.connect("city_data.db")

c = conn.cursor()

conn.commit()



#Part 1

def great_circle_distance(lat1, lon1, lat2, lon2):

    radius = 6371



    dlat = math.radians(lat2-lat1)

    dlon = math.radians(lon2-lon1)

    a = math.sin(dlat/2) * math.sin(dlat/2) + math.cos(math.radians(lat1)) 

        * math.cos(math.radians(lat2)) * math.sin(dlon/2) * math.sin(dlon/2)

    c = 2 * math.atan2(math.sqrt(a), math.sqrt(1-a))

    d = radius * c



    return d



#Part 2

def get_us_cities():

    get_city = c.execute("SELECT * FROM cities WHERE country_code = 'us'").fetchall()

    return [x for x in get_city]



#Part 3

def findDistance():

    citieslist = get_us_cities()

    lat1 = 42.8864 

    lon1 = -78.8784

    lat2 = citieslist[4]

    lon2= citieslist[5]

    distance = great_circle_distance(lat1, lon1, lat2, lon2)

    return distance 



def closest_cities():

    array = get_us_cities()

    array.sort(key = findDistance)

    return array

You're doing

array.sort(key = findDistance)

That means that the sorting algorithm is using findDistance() to find a "key" for each value it's sorting. Basically, it takes a list, does findDistance() for every item in that list, and then sorts the list according to the return values. As such, array.sort() expects that whatever it's given as a key will be able to take one value and spit out another value that can be used for sorting.

I don't know how you're structuring your database, or what format your array is going to be in, but let's assume for this example that each item in the array is a list, with indexes corresponding to the columns you listed (for example, "latitude" would be index 4, "longitude would be index 5, etc). Then, you'd want to rewrite findDistance() to take one of those as a parameter:

def findDistance(city):

    lat1 = 42.8864 

    lon1 = -78.8784

    lat2 = city[4]    # notice how we're using the variable that was passed in,

    lon2 = city[5]    #   instead of accessing get_us_cities()

    distance = great_circle_distance(lat1, lon1, lat2, lon2)

    return distance