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

#!/usr/bin/env python3
############################################################################
#
# MODULE:       v.dissolve
# AUTHOR:       M. Hamish Bowman, Dept. Marine Science, Otago University,
#                 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) 2006-2014 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.
# % keyword: vector
# % keyword: dissolve
# % keyword: area
# % keyword: line
# %end
# %option G_OPT_V_INPUT
# %end
# %option G_OPT_V_FIELD
# % label: Layer number or name.
# % 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 os
import atexit

import grass.script as grass
from grass.exceptions import CalledModuleError


def cleanup():
    nuldev = open(os.devnull, "w")
    grass.run_command(
        "g.remove",
        flags="f",
        type="vector",
        name="%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.warning(
            _(
                "No '%s' option specified. Dissolving based on category values from layer <%s>."
            )
            % ("column", layer)
        )
        grass.run_command(
            "v.extract", flags="d", input=input, output=output, type="area", layer=layer
        )
    else:
        if int(layer) == -1:
            grass.warning(
                _(
                    "Invalid layer number (%d). "
                    "Parameter '%s' specified, assuming layer '1'."
                )
                % (int(layer), "column")
            )
            layer = "1"
        try:
            coltype = grass.vector_columns(input, layer)[column]
        except KeyError:
            grass.fatal(_("Column <%s> not found") % column)

        if coltype["type"] not in ("INTEGER", "SMALLINT", "CHARACTER", "TEXT"):
            grass.fatal(_("Key column must be of type integer or string"))

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

        try:
            grass.run_command(
                "v.reclass", input=input, output=tmpfile, layer=layer, column=column
            )
            grass.run_command(
                "v.extract",
                flags="d",
                input=tmpfile,
                output=output,
                type="area",
                layer=layer,
            )
        except CalledModuleError as e:
            grass.fatal(
                _(
                    "Final extraction steps failed."
                    " Check above error messages and"
                    " see following details:\n%s"
                )
                % e
            )

    # write cmd history:
    grass.vector_history(output)


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