Multilinestrings to Linestring using Python

Question

I have a geodataframe (download link) that contains the geometry of bus lines. It is a Multilinestring. I need to transform the geometry into a single Linestring.

My first idea was to use .explode (GeoPandas).

sel = gpd.read_file(".../sel_overflow.geojson")
exp_sel = sel
exp_sel.explode()

Result:

As you can see, the .explode() splitted the Multilinestring into two Linestrings.

Furthermore, I used shapely linemerge and I got the same Multilinestring back.

from shapely.ops import linemerge

geometry = sel.loc[0, 'geometry']
shapely_object = geometry  
line = linemerge(shapely_object)
gdf = gpd.GeoDataFrame(index=[0], crs='epsg:32718', geometry=[line])

Answer 1

You could brute force it by flattening the line parts with geometry.get_coordinates().

import geopandas as gpd
from shapely.geometry import  LineString

df = gpd.read_file("sel_overflow.geojson")
print(df.head())

df.geometry = df.geometry.apply(lambda geom: LineString(gpd.GeoSeries(geom).get_coordinates()))
print(df.head())

df.to_file("sel_overflow_single.geojson")

Output:

   OBJECTID                                           geometry
0       100  MULTILINESTRING ((265097.514 8665069.813, 2650...
   OBJECTID                                           geometry
0       100  LINESTRING (265097.514 8665069.813, 265046.3 8...

It won't work for something like the following though as a linestring can only have a single start and a single end point: