[GRASS-user] python pipe Popen to grass.<?>_command

GRASS GRASS user
1

Greetings,

I’m attempting to pipe the results from:
pts=sub.Popen(‘las2txt -i %s --parse xyz --keep-classes 2 --delimiter “|” --stdout’%path, shell=True, stdout=sub.PIPE)

to the appropriate grass.?_command(‘r.in.xyz’, etc…)

i’ve tried the following:

mkInRast=grass.feed_command(“r.in.xyz”, input=pts.communicate()[0], output=‘tester’, method=‘mean’)

which results in:

Traceback (most recent call last):
File “”, line 1, in
File “/usr/lib/grass64/etc/python/grass/script/core.py”, line 198, in feed_command
return start_command(*args, **kwargs)
File “/usr/lib/grass64/etc/python/grass/script/core.py”, line 148, in start_command
return Popen(args, **popts)
File “/usr/lib/grass64/etc/python/grass/script/core.py”, line 53, in init
startupinfo, creationflags)
File “/usr/lib/python2.6/subprocess.py”, line 623, in init
errread, errwrite)
File “/usr/lib/python2.6/subprocess.py”, line 1141, in _execute_child
raise child_exception

OSError: [Errno 7] Argument list too long

Im pretty sure i’m missing something about how the Popen pipes are accessed between these two commands. Any suggestions would be most welcome.

Best,
Peter

2

Generally, this is the form that I use for python scripts and popen
(these examples are directly from working scripts of mine, but of
course you'll have to adapt them):

subprocess.Popen(
    "v.type input=%(a)s output=%(b)s type=point,centroid --overwrite" %
{'a':VECT,'b':'temp_centroid'},
    shell=True,
    stdout=subprocess.PIPE,).communicate()[0]

or if I don't need to capture data from a GRASS process I use this:

subprocess.call([
    "v.db.update",
    "map=%s" % vect,
    "layer=1","column=%s" % column,
    "value=%s" % value,
    "where=cat=%s" % cat,])

Chris

On 17 February 2011 20:36, Peter Tittmann <ptittmann@gmail.com> wrote:

Greetings,
I'm attempting to pipe the results from:
pts=sub.Popen('las2txt -i %s --parse xyz --keep-classes 2 --delimiter "|"
--stdout'%path, shell=True, stdout=sub.PIPE)

to the appropriate grass.?_command('r.in.xyz', etc...)
i've tried the following:
mkInRast=grass.feed_command("r.in.xyz", input=pts.communicate()[0],
output='tester', method='mean')
which results in:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/grass64/etc/python/grass/script/core.py", line 198, in
feed_command
return start_command(*args, **kwargs)
File "/usr/lib/grass64/etc/python/grass/script/core.py", line 148, in
start_command
return Popen(args, **popts)
File "/usr/lib/grass64/etc/python/grass/script/core.py", line 53, in
__init__
startupinfo, creationflags)
File "/usr/lib/python2.6/subprocess.py", line 623, in __init__
errread, errwrite)
File "/usr/lib/python2.6/subprocess.py", line 1141, in _execute_child
raise child_exception
OSError: [Errno 7] Argument list too long
Im pretty sure i'm missing something about how the Popen pipes are accessed
between these two commands. Any suggestions would be most welcome.
Best,
Peter

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3

Hi,

see the GRASS Programmers' manual, python section:

  http://grass.osgeo.org/programming6/pythonlib.html

specifically grass.pipe_command().

See the python scripts in grass7/scripts/ for a large number
of examples.

Hamish