Geografic-Information-System/scripts/v.dissolve/v.dissolve.py

#!/usr/bin/env python
############################################################################
#
# MODULE:       v.dissolve
# AUTHOR:       M. Hamish Bowman, Dept. Marine Science, Otago Univeristy,
#                 New Zealand
#               Markus Neteler for column support
#               Converted to Python by Glynn Clements
# PURPOSE:      Dissolve common boundaries between areas with common cat
#                 (frontend to v.extract -d)
# COPYRIGHT:    (c) 2006 Hamish Bowman, and the GRASS Development Team
#               This program is free software under the GNU General Public
#               License (>=v2). Read the file COPYING that comes with GRASS
#               for details.
#
#############################################################################

#%module
#% description: Dissolves boundaries between adjacent areas sharing a common category number or attribute.
#% keywords: vector
#% keywords: area
#% keywords: dissolve
#%end
#%option G_OPT_V_INPUT
#%end
#%option G_OPT_V_FIELD_ALL
#% label: Layer number or name. If -1, all layers are extracted.
#% required: no
#%end
#%option G_OPT_DB_COLUMN
#% description: Name of attribute column used to dissolve common boundaries
#%end
#%option G_OPT_V_OUTPUT
#%end
import sys
import os
import atexit

import grass.script as grass

def cleanup():
    nuldev = file(os.devnull, 'w')
    grass.run_command('g.remove', vect = '%s_%s' % (output, tmp), quiet = True, stderr = nuldev)

def main():
    global output, tmp

    input = options['input']
    output = options['output']
    layer = options['layer']
    column = options['column']

    #### setup temporary file
    tmp = str(os.getpid())

    # does map exist?
    if not grass.find_file(input, element = 'vector')['file']:
	grass.fatal(_("Vector map <%s> not found") % input)
    
    if not column:
	grass.run_command('v.extract', flags = 'd', input = input,
			  output = output, type = 'area', layer = layer)
    else:
        try:
            coltype = grass.vector_columns(input, layer)[column]
        except KeyError:
            grass.fatal(_('Column <%s> not found') % column)
        
	if coltype['type'] not in ('INTEGER', 'CHARACTER'):
	    grass.fatal(_("Key column must be of type integer or string"))

        f = grass.vector_layer_db(input, layer)

	table = f['table']

	tmpfile = '%s_%s' % (output, tmp)

	if grass.run_command('v.reclass', input = input, output = tmpfile,
                             layer = layer, column = column) == 0:
            grass.run_command('v.extract', flags = 'd', input = tmpfile,
                              output = output, type = 'area', layer = layer)

    # write cmd history:
    grass.vector_history(output)

if __name__ == "__main__":
    options, flags = grass.parser()
    atexit.register(cleanup)
    main()