Colorize polygons in folium

Question

I want to print some colorized polygons on a map with folium in python and I need some help. The problem I encounter is that I only get a single color for all of my polygons. Here is a part of my code I run in a loop:

import folium
from shapely.geometry import Polygon

def map_color_rsrp(rsrp):
    if (int(rsrp) in range(-70, -50)):
        return '#10FF00'
    elif (int(rsrp) in range(-90, -70)):
        return 'green'
    elif (int(rsrp) in range(-110, -90)):
        return 'blue'
    elif (int(rsrp) in range(-130, -110)):
        return '#FF7000'
    else:  # range(-150, -130)
        return 'grey'

# create map
grid_map = folium.Map((51.443787, 7.262206), zoom_start=14)

# create FeatureGroups for RSRP & RSRQ
rsrp_grid_fg = folium.FeatureGroup(name="RSRP", overlay=True)

grid_poly_rows = [
    [-78.2,  [(7.251043000000002, 51.444325000000035), (7.251043000000002, 51.44462500000004), (7.251343000000002, 51.44462500000004), (7.251343000000002, 51.444325000000035)]],
    [-89.3,  [(7.251343000000002, 51.444325000000035), (7.251343000000002, 51.44462500000004), (7.251643000000002, 51.44462500000004), (7.251643000000002, 51.444325000000035)]],
    [-113.7, [(7.251643000000002, 51.44402500000003), (7.251643000000002, 51.444325000000035), (7.2519430000000025, 51.444325000000035), (7.2519430000000025, 51.44402500000003)]],
    [-112.3, [(7.251643000000002, 51.444325000000035), (7.251643000000002, 51.44462500000004), (7.2519430000000025, 51.44462500000004), (7.2519430000000025, 51.444325000000035)]],
    [-133.7, [(7.2519430000000025, 51.44402500000003), (7.2519430000000025, 51.444325000000035), (7.252243000000003, 51.444325000000035), (7.252243000000003, 51.44402500000003)]]
]

for row in grid_poly_rows:
    mean_rsrp = row[0]
    rsrp_tooltip_str = str(mean_rsrp)
    rsrp_color = map_color_rsrp(mean_rsrp)
    style_ = {
        'fillColor': rsrp_color,
        'color': rsrp_color,
        'weight': 1,
        'fillOpacity': 0.5}
    folium.GeoJson(Polygon(row[1]),
                   style_function=lambda x: style_,
                   tooltip=rsrp_tooltip_str
                   ).add_to(rsrp_grid_fg)

rsrp_grid_fg.add_to(grid_map)

# add LayerControl
folium.LayerControl(collapsed=False).add_to(grid_map)

grid_map.save(outfile="grid.html")

I think I got something wrong with the style_function. Any advice is appreciated! Thanks in advance!

Cheers ninjab3s

Answer 1

I made it work! I found this post https://stackoverflow.com/a/53816162/13872164, which explains that the lambda style function is not executed immediately. The following changes made my code work:

for row in grid_poly_rows:
    mean_rsrp = row[0]
    rsrp_tooltip_str = str(mean_rsrp)
    folium.GeoJson(Polygon(row[1]),
                   style_function=lambda x, mean_rsrp=mean_rsrp: {
                'fillColor': map_color_rsrp(mean_rsrp),
                'color': map_color_rsrp(mean_rsrp),
                'weight': 1,
                'fillOpacity': 0.5},
                   tooltip=rsrp_tooltip_str
                   ).add_to(rsrp_grid_fg)

Next time Ill dig deeper before I post