I have a shapefile dataset of polygons. I would like to find those polygons that are completely surrounded/enclosed. Mathematically, this means that the perimeter of Polygon A should equal the sum of the line segments of its neighboring polygons B,C,D,E,...n+1. If they are NOT completely enclosed, then the perimeter of Polygon A /= the sum of intersecting line segments of neighboring polygons B,C,D,E...n+1.
The polygons are irregularly shaped and not always square, so there aren't always the same # of polygon neighbors.
I found this post discussing how to do this in SQL, but I'd like to know how to write something similar in PyQGIS 3. (Determine if a polygon is not enclosed by other polygons).
I'm new at Python programming, but I imagine I basically need to:
- import pyQGIS libraries
- iface select active layer
- calculate new perimeter field (data is in planar proj)
- loop for every polygon in active layer: *select polygons that intersect *sum intersecting line lengths *create new field of summed intersection lengths *select where the two fields are equal
Is there a way to do this in QGIS? Would I need to convert to lines first?