How to draw a world map in folium and indicate some countries on it?

Question

can someone tell me how to draw a world map and indicate 10-15 countries on it using matplotlib/folium ? I downloaded 'world-countries.json', so got world map (in Jupyter notebooks):

    import folium 
    import json
    import pandas as pd
    import pathlib
    
    world_path = pathlib.Path('world-countries.json')
    
    with open(world_path) as f:
        world = json.load(f)
    
    from folium import GeoJson
    m = folium.Map(tiles=None)
    GeoJson(world).add_to(m)
    
    data = pd.read_csv('15_countires.csv')
    data.shape

    map.choropleth(geo_data=world_path, data=data,
             columns=['CountryCode'],
             key_on='feature.id',
             fill_color='YlGnBu', fill_opacity=0.7, line_opacity=0.2)

But how to indicate countries on it and color them ? Or, maybe, I can do it without geojson, only using folium ?

Answer 1

Took this a bit further than the question. It is very simple to do

1. it's better if each country is overlaid in different colours. So I got the country colours from wikipedia page. This is the bulk of the code, sourcing this.
2. there are missing countries in world-countries.json. Notably where I reside..
3. I used pandas mostly because I'm familiar with it for preparing and then using the data.

import requests, json, re, folium
from bs4 import BeautifulSoup
import pandas as pd

# dynamically get the world-country boundaries 
res = requests.get("https://raw.githubusercontent.com/python-visualization/folium/master/examples/data/world-countries.json")
df = pd.DataFrame(json.loads(res.content.decode()))
df = df.assign(id=df["features"].apply(pd.Series)["id"],
         name=df["features"].apply(pd.Series)["properties"].apply(pd.Series)["name"])

# build a dataframe of country colours scraped from wikipedia
resp = requests.get("https://en.wikipedia.org/wiki/National_colours",)
soup = BeautifulSoup(resp.content.decode(), "html.parser")
colours = []
for t in soup.find_all("table", class_="wikitable"):
    cols = t.find_all("th")
    ok = (len(cols)>5 and cols[0].string.strip()=="Country" and cols[4].string.strip()=="Primary")
    if ok:
        for tr in t.find_all("tr"):
            td = tr.find_all("td")
            if len(td)>5:
                sp = td[4].find_all("span")
                c1 = re.sub("background-color:([\w,#,0-9]*).*", r"\1", sp[0]["style"])
                c2 = c1 if len(sp)==1 else re.sub("background-color:([\w,#,0-9]*).*", r"\1", sp[1]["style"])
                colours.append({"country":td[0].find("a").string, 
                                "colour1":c1,
                                "colour2":c2,

                               })
dfc = pd.DataFrame(colours).set_index("country")  

# a list of interesting countries - Singapore is missing!
countries = ["Singapore","Malaysia","Indonesia","Vietnam","Philippines"]

# style the overlays with the countries own colors...
def style_fn(feature):
    cc = dfc.loc[feature["properties"]["name"]]
    ss= {'fillColor':f'{cc[0]}', 'color':f'{cc[1]}'}
    return ss

# create the base map
m = folium.Map(location = [1.34, 103.82],
               zoom_start=6,
               control_scale=True)

# overlay desired countries over folium map
for r in df.loc[df["name"].isin(countries)].to_dict(orient="records"):
    folium.GeoJson(r["features"], name=r["name"], tooltip=r["name"], style_function=style_fn).add_to(m)

m