Python shapely difference between two polygons

Question

I have a geometry question using shapely,Fiona and polygons shapefiles with big data(over 700000 features any polygon shapefile).

polygon1.difference(polygon2)

I want to find the difference between two polygons using shapely (or maybe geopandas?) and I have read this post, I want the difference calculate only in the polygons segments(lines) and not the polygon geometry.

for example if I use code from the post with add more lines the final export difference is a polygon layer,I want the line layer to show me the differences between two polygons.

with the light blue line is the difference.

that because I think is more fast the difference calculator to create lines from polygons.

Answer 1

Once you've calculated the difference between your polygons (let's call this delta), take the difference between the exterior of delta and the exterior of your brown polygon2: result = delta.exterior.difference(polygon2.exterior). Note that the sense of the difference will be significant and it may be tricky to generalize this to all possible polygons. Good luck!