[GRASS-dev] pygrass: append new point to map of points

GRASS GIS GRASS GIS developer
1

Hello,

Is it possible in pygrass to append a new point to a map of points (same for other features) ? Or do I have to get all the features of a map, and the new feature, and then write all features to a new map ?

Moritz

2

Soory for the delay,

On Fri, Jan 30, 2015 at 3:52 PM, Moritz Lennert
<mlennert@club.worldonline.be> wrote:

Is it possible in pygrass to append a new point to a map of points (same for
other features) ? Or do I have to get all the features of a map, and the new
feature, and then write all features to a new map ?

Yes, here an example, write a new map:

{{{

from grass.pygrass.vector.geometry import Point
from grass.pygrass.vector import VectorTopo
with VectorTopo('mypoits', mode='w') as my:

... my.write(Point(0, 10))
... my.write(Point(5, 15))
...

}}}

read an existing map:

{{{

with VectorTopo('mypoits', mode='r') as my:

... for p in my:
... print(p)
...
POINT(0.000000 10.000000)
POINT(5.000000 15.000000)
}}}

Add some new point to an existing map:

{{{

with VectorTopo('mypoits', mode='rw') as my:

... my.write(Point(10, 10))
... my.write(Point(15, 15))
...
}}}

and read again the modified map:

{{{

with VectorTopo('mypoits', mode='r') as my:

... for p in my:
... print(p)
...
POINT(0.000000 10.000000)
POINT(5.000000 15.000000)
POINT(10.000000 10.000000)
POINT(15.000000 15.000000)
}}}

All the best

Pietro

3

Hi,

2015-01-31 11:16 GMT+01:00 Pietro <peter.zamb@gmail.com>:

Yes, here an example, write a new map:

btw, are these examples collected somewhere (on the wiki)? Thanks! Martin

--
Martin Landa
http://geo.fsv.cvut.cz/gwiki/Landa
http://gismentors.eu/mentors/landa

4

Hi Martin,

On Sat, Jan 31, 2015 at 12:10 PM, Martin Landa <landa.martin@gmail.com> wrote:

Hi,

2015-01-31 11:16 GMT+01:00 Pietro <peter.zamb@gmail.com>:

Yes, here an example, write a new map:

btw, are these examples collected somewhere (on the wiki)? Thanks! Martin

I collected some training material here:

http://grasswiki.osgeo.org/wiki/Python/pygrass

and here there is a tutorial for the vector part:

http://nbviewer.ipython.org/github/zarch/workshop-pygrass/blob/master/02_Vector.ipynb

But yes the documentation for the pygrass library is not enough I hope
to be able to fill this gap in the next months.

Pietro

5

Hi Pietro,

2015-01-31 14:42 GMT+01:00 Pietro <peter.zamb@gmail.com>:

I collected some training material here:

http://grasswiki.osgeo.org/wiki/Python/pygrass

thanks for that. Martin

--
Martin Landa
http://geo.fsv.cvut.cz/gwiki/Landa
http://gismentors.eu/mentors/landa