#!/usr/bin/env python
#****************************************************************
#*
#* MODULE:     v.somma, v 1.0.0
#*
#* AUTHOR(S):  Antonio Alliegro
#*
#* PURPOSE:    Calcola la somma dei valori di una colonna di
#*             tipo numerico
#*
#* COPYRIGHT:  (C) 2011 Antonio Alliegro Civil Engineer
#*             Salerno, Italy
#*             antonioall(at)libero.it
#*
#*             First Version: 2011/06/02
#*             Last  Version: 2011/06/02
#*
#*             This program is free software under the
#*             GNU General Public License (>=v2).
#*             Read the file COPYING that comes with GRASS
#*             for details.
#*
#****************************************************************

#%module
#% description: Calcola la somma dei valori di una colonna di tipo numerico
#% keywords: vector
#%end

#%option
#% key: map
#% type: string
#% gisprompt: old,vector,vector
#% key_desc: nome
#% description: Nome copertura vettoriale
#% required: yes
#%end

#%option
#% key: colonna
#% type: string
#% key_desc: colonna
#% description: Nome colonna
#% required : yes
#% gisprompt: old_dbcolumn,dbcolumn,dbcolumn
#%end

import sys, time
import grass.script as grass

def main():
    copertura = options['map']
    colonna = options['colonna']
    somma = 0.00

    ret = grass.read_command('v.db.select',
                             map = copertura,
                             columns = colonna,
                             flags = 'c')
    
    if ret == {}:
        grass.fatal("Errore nella lettura dei dati della colonna")
    
    vettore = ret.split('\n')
    for v in vettore:
        if v != '':
            somma += float(v)
        
    grass.message("Somma: %15f" % somma)
        
    return 0
    #End main

if __name__ == "__main__":
    options, flags = grass.parser()
    sys.exit(main())