[GRASS-user] SQL query in Python script

[Charlie Shobe]

Hi all,

I am attempting to extract a subset of points from a points vector based on
the values in the column "dir". I am running GRASS 6.4.4 on Mac OS 10.9.5.

In the GRASS command line, I can successfully make my selection with the
following command:
--------------------------------------------------------------
GRASS 6.4.4 (Yellowstone):~ > *v.extract input=streams_points
output=outlets_vect type=point where="dir<0"*

92 categories loaded from table <streams_points>

Extracting features...

Building topology for vector map <outlets_vect>...

Registering primitives...

92 primitives registered

92 vertices registered

Building areas...

 100%

0 areas built

0 isles built

Attaching islands...

Attaching centroids...

 100%

Number of nodes: 92

Number of primitives: 92

Number of points: 92

Number of lines: 0

Number of boundaries: 0

Number of centroids: 0

Number of areas: 0

Number of isles: 0

Writing attributes...

v.extract complete.

-------------------------------------------------------
However, due to my incomplete knowledge of how Python and SQL interact, I
am having trouble executing the same command in a Python script. Here is
what I am trying:

*g.run_command("v.extract", input="streams_points", output="outlets_vect",
type="point", where="dir<0")*

When I run this command, it fails to extract any points. I know that this
must be due to some problem with the syntax of my SQL statement.

Can anyone clear this up for me?

Thanks,

Charlie
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/grass-user/attachments/20141130/1fe5439a/attachment-0001.html>