Module 6: Geometries

 This week’s assignment in GIS Programming focused on extracting detailed geometry information from a shapefile and writing it to a plain text file using Python and ArcPy. The objective was to loop through a shapefile called rivers.shp, extract each feature’s object ID, name, and every individual vertex coordinate (X, Y), then write that data into a structured .txt file.

We began by setting up our script environment; importing arcpy, enabling overwrite output, and setting the workspace to the Module 6 data folder. From there, we created a search cursor that accessed the OID, SHAPE geometry object, and river name for each feature. Then, we opened a .txt file.

One key learning moment was understanding how to use SHAPE@ instead of SHAPE@XY. The SHAPE@ token gives us full access to the geometry object, which allowed us to use the .getPart() method to loop through each point (or vertex) that defines the shape of the river features.

Inside a nested loop, we tracked each vertex using a simple counter and wrote the following values to the text file: feature ID, vertex ID, X coordinate, Y coordinate, and river name. A newline character (\n) was used to ensure each set of data appeared on its own line for readability.

This exercise helped reinforce how vector geometries are structured in shapefiles and how to programmatically access and work with that data. I now feel more confident handling feature geometry in Python, and I see how this could be useful.