[GRASS-dev] Python Scripting

Glynn Clements glynn at gclements.plus.com
Fri Jul 18 13:20:46 EDT 2008


Glynn Clements wrote:

> > As to existing modules, what about a helper function to access then?
> > 
> > module.executeModule( name="r.stats", options={ "input": 
> > "elevation.dem,slope,aspect", "fs": ",", "output": "elev.csv"}, 
> > flags=["q", "1", "n", "g"] )
> 
> This idea has occurred to me. Some comments:
> 
> Pass argument values as Python values, e.g. passing multiple values as
> lists, passing numeric types directly, etc, and have the interface
> convert them to strings. Pass the flags as a single string.
> 
> module.execute( "r.stats",
>                 options = { "input": ["elevation.dem", "slope", "aspect"],
>                             "fs": ",",
>                             "output": "elev.csv" },
>                 flags = "q1ng" )
> 
> Provide a lower-level function which simply generates the command to
> pass to Popen(), for cases where you want to interact with the child
> process.

I have attached a first draft of such a module, which also includes a
wrapper function for g.parser (for which an example script is also
attached).

-- 
Glynn Clements <glynn at gclements.plus.com>

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import os
import os.path
import sys
import types
import subprocess

def _make_val(val):
    if isinstance(val, types.StringType):
	return val
    if isinstance(val, types.ListType):
	return ",".join(map(_make_val, val))
    if isinstance(val, types.TupleType):
	return _make_val(list(val))
    return str(val)

def make_command(prog, options = [], flags = "", overwrite = False, quiet = False, verbose = False):
    args = [prog]
    if overwrite:
	args.append("--o")
    if quiet:
	args.append("--q")
    if verbose:
	args.append("--v")
    if flags:
	args.append("-%s" % flags)
    for opt, val in options.iteritems():
	args.append("%s=%s" % (opt, _make_val(val)))
    return args

def start_command(prog, options = [], flags = "", overwrite = False, quiet = False, verbose = False, **kwargs):
    args = make_command(prog, options, flags, overwrite, quiet, verbose)
    return subprocess.Popen(args, **kwargs)

def run_command(*args, **kwargs):
    ps = start_command(*args, **kwargs)
    return ps.wait()

def _parse_env():
    options = {}
    flags = {}
    for var, val in os.environ.iteritems():
	if var.startswith("GIS_OPT_"):
	    opt = var.replace("GIS_OPT_", "", 1).lower()
	    options[opt] = val;
	if var.startswith("GIS_FLAG_"):
	    flg = var.replace("GIS_FLAG_", "", 1).lower()
	    flags[flg] = bool(int(val));
    return (options, flags)

def parser():
    if not os.getenv("GISBASE"):
        print >> sys.stderr, "You must be in GRASS GIS to run this program."
        sys.exit(1)

    if len(sys.argv) > 1 and sys.argv[1] == "@ARGS_PARSED@":
	return _parse_env()

    argv = sys.argv[:]
    name = argv[0]
    if not os.path.isabs(name):
	argv[0] = os.path.normpath(os.path.join(sys.path[0], name))

    os.execvp("g.parser", [name] + argv)
    raise OSError("error executing g.parser")
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#!/usr/bin/env python

# g.parser demo script for python programing

import grass

#%Module
#%  description: g.parser test script (python)
#%End
#%flag
#%  key: f
#%  description: a flag
#%END
#%option
#% key: raster
#% type: string
#% gisprompt: old,cell,raster
#% description: raster input map
#% required : yes
#%end
#%option
#% key: vector
#% type: string
#% gisprompt: old,vector,vector
#% description: vector input map
#% required : yes
#%end
#%option
#% key: option1
#% type: string
#% description: an option
#% required : no
#%end
    
if __name__ == "__main__":
    (options, flags) = grass.parser()

    print ""
    if flags['f']:
        print "Flag -f set"
    else:
        print "Flag -f not set"

    #test if parameter present:
    if options['option1']:
        print "Value of option1: '%s'" % options['option1']

    print "Value of raster= option: '%s'" % options['raster']
    print "Value of vector= option: '%s'" % options['vector']


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