Plot maps in python error : no arguments in initialization list

Question

From the following files I want to do a map plot by using folium:

Polygons file: https://drive.google.com/file/d/1uhj7OyHktPseR_CtRD0vPfq8HziHA4RK/view? Postcode variable level: https://drive.google.com/file/d/1oFBITKzqLyTvQEASmZmO6CGCOzdPacgH/view?

Attempt1 (folium):

import pandas as pd
import geopandas as gpd
import folium

df_postcode_variable = pd.read_csv("postcode_sample.csv", dtype=str)  # Postcode variable level
df_postcode_variable['people'] = df_postcode_variable['people'].astype(float)
df_polygons = gpd.read_file("postcode_polygons.shp") # Polygons file
df_polygons.crs = "EPSG:4326"

my_map = folium.Map(location=[41.3890727,2.1572654], zoom_start=13,
                   detect_retina=True, control_scale=False)

folium.Choropleth(
        geo_data=df_polygons,
        name='choropleth',
        data=df_postcode_variable,
        columns=['cp','people'],
        key_on='cp',
        fill_color='OrRd',
        fill_opacity=0.5,
        line_opacity=0.8,
        line_color='Blue',
        legend_name='number of people'
    ).add_to(my_map)

my_map

But I get the following error:

ValueError: key_on `'cp'` not found in GeoJSON.

Attempt 2(pandas_bokeh) working:

import pandas_bokeh
pandas_bokeh.output_notebook()

df_joined=df_polygons.merge(df_postcode_variable.set_index('cp'), on='cp')

df_joined.plot_bokeh(simplify_shapes=20000,
                  category="people", 
                  colormap="Spectral", 
                  hovertool_columns=["cp","people"])

How could I fix this error on folium? cp is in both objects so, It doesnt make sense to me. It seems that is not thetecting cp in df_polygons.

Answer 1

If the geodata is in geopandas format, the key is specified as feature.properties.column_name, as in geojson. See this for details.

my_map = folium.Map(location=[41.3890727,2.1572654], zoom_start=12,
                   detect_retina=True, control_scale=False)

folium.Choropleth(
        geo_data=df_polygons,
        name='choropleth',
        data=df_postcode_variable,
        columns=['cp','people'],
        key_on='feature.properties.cp',
        fill_color='OrRd',
        fill_opacity=0.5,
        line_opacity=0.8,
        line_color='Blue',
        legend_name='number of people'
    ).add_to(my_map)

my_map