The following steps will serve as a guideline to create a choropleth using available data on an internet page:

Load the notebook with commands developed in step 1.1. (click on the link):

https://colab.research.google.com/drive/1BGUOYlSMjsupiz3_lhm9PD1LwwSKSUhg?usp=sharing

JSON stands for JavaScript Object Notation. It is a text format for storing and transporting data. JSON is "self-describing" and easy to understand. The following code gives an example of how to create a variable in a JSON format:

person = {

    "firstName": "Jane",

    "lastName": "Doe",

    "hobbies": ["running", "sky diving", "singing"],

    "age": 35,

    "children": [

        {

            "firstName": "Alice",

            "age": 6

        },

        {

            "firstName": "Bob",

            "age": 8

        }

    ]

}

person

This command produces the following figure:

Accessing the elements of a JSON

To access specific data in a JSON variable the following commands could be employed. As you can see, JSON supports primitive types, like strings and numbers, as well as nested lists and objects. Wait, that looks like a Python dictionary! Let's check how to access some parts of the data.

print(person['firstName'])

print(person['children'][0])

print(person['children'][0]['firstName'])

The following result will be produced:

Jane {'firstName': 'Alice', 'age': 6} Alice 

Obtaining a GEOJSON format file

In the next example, it is possible to extract JSON data from a webpage (using command requests.get) and store it at a variable r. Then, it is possible to convert the variable r content into a JSON format file (using the command r.json) and store it at a variable wdcs.

import json

import requests

url = "https://s3-api.us-geo.objectstorage.softlayer.net/cf-courses-data/CognitiveClass/DV0101EN/labs/Data_Files/world_countries.json"

r = requests.get(url)

wdcs = r.json()

wdcs

This will produce the result:

{'type': 'FeatureCollection', 'features': [{'type': 'Feature', 'properties': {'name': 'Afghanistan'}, 'geometry': {'type': 'Polygon', 'coordinates': [[[61.210817, 35.650072], [62.230651, 35.270664], [62.984662, 35.404041], [63.193538, 35.857166], [63.982896, 36.007957], [64.546479, 36.312073], [64.746105, 37.111818], [65.588948, 37.305217], ...

Obtaining the name of the countries

It is possible extract the name of all countries loaded from the Web Page. Using the keyword 'features' it is possible to select each country and its correspoding properties as done in the following code. 

# Extracting properties of each country

for country in wdcs['features']:

  print(country['properties'])

This will produce the following result:

{'name': 'Afghanistan'} {'name': 'Angola'} {'name': 'Albania'} {'name': 'United Arab Emirates'} {'name': 'Argentina'} {'name': 'Armenia'} {'name': 'Antarctica'} {'name': 'French Southern and Antarctic Lands'} {'name': 'Australia'} {'name': 'Austria'} {'name': 'Azerbaijan'} {'name': 'Burundi'} {'name': 'Belgium'} {'name': 'Benin'} {'name': 'Burkina Faso'} {'name': 'Bangladesh'} {'name': 'Bulgaria'} {'name': 'The Bahamas'} {'name': 'Bosnia and Herzegovina'} {'name': 'Belarus'} {'name': 'Belize'} {'name': 'Bolivia'} {'name': 'Brazil'}  ...

Extracting the borders information of each country

For each country, it is possible to extract its corresponding geometry which is represented by an identifier type ('Polygon' or 'MultiPolygon') and a list of pairs (lists) of latitude and longitude points that delimits country borders. 

# Extracting properties of each country

for country in wdcs['features']:

  print(country['geometry'])

This will produce:

{'type': 'Polygon', 'coordinates': [[[61.210817, 35.650072], ...]]} 

{'type': 'MultiPolygon', 'coordinates': [[[[16.326528, -5.87747], ...]]]} 

{'type': 'Polygon', 'coordinates': [[[20.590247, 41.855404], ...]]} 

Drawing each country's borders on a map using the JSON with the country's data

import folium

map = folium.Map(location=[30,10], zoom_start=3, tiles = 'cartodbpositron')

folium.GeoJson(wdcs).add_to(map)

map

This will generate the following map: