[GRASS-user] Creating a new vector map with pygrass

GRASS GRASS user
1

Hello!

Here is yet another request for hand-holding with GRASS GIS. This time it’s a question on pygrass API, version 7.8.5. I want to create a new vector map from a Python script. The steps I’m following are:

  1. Create a VectorTopo object with.

  2. Define attribute columns: cols = [(column name, type), …]

  3. Open the VectorTopo object in write mode: write(“w”, tab_cols=cols, …).

  4. Add geometry objects, in my case it’s Area objects, one by one using write() interface.

  5. Commit changes and close the VectorTopo.

Step 4, however, is causing “AttributeError” in a pygrass module. Stack trace:

Traceback (most recent call last):
File “stream_features.py”, line 404, in
generateWatersheds(ssegs, dwsmapname)
File “stream_features.py”, line 359, in generateWatersheds
dwsvector.write(
File “/Applications/GRASS-7.8.app/Contents/Resources/etc/python/grass/pygrass/errors.py”, line 15, in wrapper
return method(self, *args, **kargs)
File “/Applications/GRASS-7.8.app/Contents/Resources/etc/python/grass/pygrass/vector/init.py”, line 217, in write
result = self._write_area(geo_obj)
AttributeError: ‘VectorTopo’ object has no attribute ‘_write_area’

Can someone shed light on where my understanding is going wrong? Is this a bug in vector/init.py? The code snippet for reference:

dwsvector = vector.VectorTopo(“differential_watersheds”)

dwscols = [(“cat”, “INTEGER PRIMARY KEY”),
(“stream1”, “INTEGER”),
(“stream2”, “INTEGER”)]

dwsvector.open(“w”, tab_name=dwsmapname, tab_cols=dwscols, overwrite=True)

cat = 1

“boundary” is a vector.geometry.Boundary object, obtained

from an existing vector map that is opened previously.

areageom = vector.geometry.Area(v_id=boundary.id, c_mapinfo=boundary.c_mapinfo)

dwsvector.write(
areageom,
cat,
attrs=(boundary.attrs[“s1”], boundary.attrs[“s2”]))

The AttributeError thrown when the write() method above is invoked.

Hope the problem description is clear, if it isn’t, please let me know.

Asim