Drop Linestring geometry from a GeoDataFrame

Question

I try to create a shapefile of the FAO/GAUL/2015/leve1 country regions of the LMIC's countries. For that I decided to use Python as it gave me access to the earthengine API and the geopandas librairy.

To create the geodataframe I proceed as such :

import ee 
import geemap
import geopandas as gpd

ee.Initialize()

for i, row in df.iterrows():
    # select the country
    ee_country = ee.FeatureCollection("FAO/GAUL/2015/level1").filter(ee.Filter.eq('ADM0_CODE', row.GAUL))
    country_json = geemap.ee_to_geojson(ee_country)
    tmp = gpd.GeoDataFrame.from_features(country_json)
    
    # add the country to the global gdf 
    gdf = tmp if i == 0 else pd.concat([gdf, tmp])
 
gdf.crs = "EPSG:4326"
gdf

(the df is containing the FAO GAUL ADM0_CODE)

Then I try to transform this GDF into a shapefile using

gdf.to_file('FAO_GAUL_2015_level1.shp')

But I get an error because I have shapely.geometry.collection.GeometryCollection in my gdf (with linestring embed so not shapelyfiable).

Is there a way to only kee the Polygon for revery lin that contain a Geometry collection ? or Is it possible to drop all the linestring from the geometry column ?

Answer 1

I created a workaround that replace each line of the gdf containing a geometryCollection (a linestring + a polygon) by its first polygon

You can customize it to better fit your requirements

gdf_filtered = gdf.copy()

for i, row in gdf.iterrows():
    if type(row.geometry) == shapely.geometry.collection.GeometryCollection:

        # get the polygon and only keep the polygon 
        for shape in row.geometry:
            if type(shape) == shapely.geometry.polygon.Polygon:
                gdf_filtered.at[i, 'geometry'] = shape
                break

Answer 2

As per the answer, but if you want all polygons rather than just one then use:

gdf_filtered = gdf.copy()

for i, row in gdf.iterrows():
    if type(row.geometry) == shapely.geometry.collection.GeometryCollection:

        # get all polygons
        shapes = []
        for shape in row.geometry:
            if type(shape) == shapely.geometry.polygon.Polygon:
                shapes.append(shape)
        gdf_filtered.at[i, 'geometry'] = shapely.geometry.collection.GeometryCollection(shapes)

Answer 3

You can drop all LineStrings from the geometry column like this:

gdf = gdf[gdf.geometry.type != 'LineString']

If you want to split multipart geometries into single part geometries use

gdf.explode()