[GRASS-user] Use of v.in.ascii in python with stdin

[Johannes Radinger]

Hi,


On Mon, Jun 17, 2013 at 3:39 PM, Pietro <peter.zamb at gmail.com> wrote:

> Hi Johannes,
>
> On Mon, Jun 17, 2013 at 1:24 PM, Johannes Radinger
> <johannesradinger at gmail.com> wrote:
> > I want to create a point via python at a specific location using the
> > v.in.ascii command. How can I also specify the colum names or how can a
> > header be used in combination with the standard input. As it is only one
> > single point I don't want to create a txt file containing the header and
> the
> > info. I tried following in GRASS7:
>
> I think that some of your parameters are not correct...
>
> {{{
> from grass.pygrass.modules import Module
>
> ASCII = """cat,X,Y,Name
> 1,635828.3,223067.0,pub
> 2,643553.4,220711.5,pizzeria"""
>
> COLS = 'cat int, x double precision, y double precision, name varchar(10)'
>
> vina = Module('v.in.ascii', input='-', output='pnt__v_in_ascii',
>                         format='point', separator=',', skip=1, x=2, y=3,
> cat=1,
>                         columns=COLS, stdin_=ASCII, overwrite=True,
> finish_=True)
> }}}
>
>

I thought I found the problem by seeing the difference between the
parameter: "stdin_" and
"stdin". However here the result with "_":

grass.write_command("v.in.ascii",
        overwrite=True,
        format="point",
        #flags="n",
        input="-",
        cat=1,
        x=2,
        y=3,
        stdin_=ascii,
        columns=cols,
        output="mypoint",
        separator=",")
Traceback (most recent call last):
  File "<input>", line 12, in <module>
  File "/usr/local/grass-7.0.svn/etc/python/grass/script/core.py", line
331, in write_command
    stdin = kwargs['stdin']
KeyError: 'stdin'

So I tried without:

ascii = """cat,X,Y,Name
1,10:20:08E,53:25:27N,mypoint"""

cols = 'cat int, x varchar(10), y varchar(10), name varchar(10)'

grass.write_command("v.in.ascii",
        overwrite=True,
        format="point",
        #flags="n",
        input="-",
        cat=1,
        x=2,
        y=3,
        stdin=ascii,
        columns=cols,
        output="mypoint",
        separator=",")

which at least executes but gives me following error:
GRASS_INFO_ERROR(13239,2): Unparsable longitude value in column num 2: X

Everything seems to be similar to your example except for the fact that I
am using lat/long values instead of projected double precision X
Y coordinates.




> Mostly with the same parameters you can run grass.write_command.
> But If you are looking for a tool to "play" and experiment I highly
> suggest pygrass:
>
> {{{
> from grass.pygrass.vector import VectorTopo
> from grass.pygrass.geometry import Point
>
> new = VectorTopo('mynewvect')
> COLS = [(u'cat',       'INTEGER PRIMARY KEY'),  (u'name',      'VAR CHAR')]
> new.open('w', tab_cols=COLS)
> new.write(Point(635828.3, 223067.0), ('pub', ))
> new.write(Point(643553.4, 220711.5), ('restaurant', ))
> new.close()
>
> new.open('r')
> new.cat(1).attrs['name']  # return: pub
> new.close()
> }}}
>
> If you are interested please have a look of the ipython notebook:
>
> https://github.com/zarch/workshop-pygrass
>
> you have just to clone, and from a running session of grass enter in
> the directory and launch:
>
> > ipython notebook
>
> to have a briefly introduction to the library.
>
> Have fun!
>
> Pietro
>
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