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"""!@package grass.script.db
@brief GRASS Python scripting module (database functions)
Database related functions to be used in Python scripts.
Usage:
@code
from grass.script import db as grass
grass.db_describe(table)
...
@endcode
(C) 2008-2009 by 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.
@author Glynn Clements
@author Martin Landa <landa.martin gmail.com>
"""
import tempfile as pytempfile # conflict with core.tempfile
from core import *
# i18N
import gettext
gettext.install('grasslibs', os.path.join(os.getenv("GISBASE"), 'locale'), unicode=True)
def db_describe(table, **args):
"""!Return the list of columns for a database table
(interface to `db.describe -c'). Example:
\code
>>> grass.db_describe('lakes')
{'nrows': 15279, 'cols': [['cat', 'INTEGER', '11'], ['AREA', 'DOUBLE PRECISION', '20'],
['PERIMETER', 'DOUBLE PRECISION', '20'], ['FULL_HYDRO', 'DOUBLE PRECISION', '20'],
['FULL_HYDR2', 'DOUBLE PRECISION', '20'], ['FTYPE', 'CHARACTER', '24'],
['FCODE', 'INTEGER', '11'], ['NAME', 'CHARACTER', '99']], 'ncols': 8}
\endcode
@param table table name
@param args
@return parsed module output
"""
s = read_command('db.describe', flags = 'c', table = table, **args)
if not s:
fatal(_("Unable to describe table <%s>") % table)
cols = []
result = {}
for l in s.splitlines():
f = l.split(':')
key = f[0]
f[1] = f[1].lstrip(' ')
if key.startswith('Column '):
n = int(key.split(' ')[1])
cols.insert(n, f[1:])
elif key in ['ncols', 'nrows']:
result[key] = int(f[1])
else:
result[key] = f[1:]
result['cols'] = cols
return result
# run "db.connect -p" and parse output
def db_connection():
"""!Return the current database connection parameters
(interface to `db.connect -p'). Example:
\code
>>> grass.db_connection()
{'group': 'x', 'schema': '', 'driver': 'dbf', 'database': '$GISDBASE/$LOCATION_NAME/$MAPSET/dbf/'}
\endcode
@return parsed output of db.connect
"""
s = read_command('db.connect', flags = 'p')
return parse_key_val(s, sep = ':')
def db_select(sql = None, filename = None, table = None, **args):
"""!Perform SQL select statement
Note: one of <em>sql</em>, <em>filename</em>, or <em>table</em>
arguments must be provided.
Examples:
\code
grass.db_select(sql = 'SELECT cat,CAMPUS FROM busstopsall WHERE cat < 4')
(('1', 'Vet School'), ('2', 'West'), ('3', 'North'))
\endcode
\code
grass.db_select(filename = '/path/to/sql/file')
\endcode
Simplyfied usage
\code
grass.db_select(table = 'busstopsall')
\endcode
performs <tt>SELECT * FROM busstopsall</tt>.
@param sql SQL statement to perform (or None)
@param filename name of file with SQL statements (or None)
@param table name of table to query (or None)
@param args see db.select arguments
"""
fname = tempfile()
if sql:
args['sql'] = sql
elif filename:
args['input'] = filename
elif table:
args['table'] = table
else:
fatal(_("Programmer error: '%(sql)s', '%(filename)s', or '%(table)s' must be provided") %
{'sql': 'sql', 'filename': 'filename', 'table': 'table'} )
if 'fs' not in args:
args['fs'] = '|'
ret = run_command('db.select', quiet = True,
flags = 'c',
output = fname,
**args)
if ret != 0:
fatal(_("Fetching data failed"))
ofile = open(fname)
result = map(lambda x: tuple(x.rstrip(os.linesep).split(args['fs'])),
ofile.readlines())
ofile.close()
try_remove(fname)
return tuple(result)
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