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# -*- coding: utf-8 -*-
"""
***************************************************************************
ogrds.py
---------------------
Date : November 2012
Copyright : (C) 2012 by Victor Olaya
Email : volayaf at gmail dot com
***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************
"""
__author__ = 'Victor Olaya'
__date__ = 'November 2012'
__copyright__ = '(C) 2012, Victor Olaya'
# This will get replaced with a git SHA1 when you do a git archive
__revision__ = '$Format:%H$'
from osgeo import ogr
class OgrDs:
def __init__(self, format, ds):
self.open(format, ds)
def open(self, format, ds):
driver = ogr.GetDriverByName(format)
self.ds = driver.CreateDataSource(ds)
return self.ds
def close(self):
if self.ds is not None:
self.ds.Destroy()
def execute_sql(self, sql_statement):
poResultSet = self.ds.ExecuteSQL(sql_statement, None, None)
if poResultSet is not None:
self.ds.ReleaseResultSet(poResultSet)
def select_values(self, sql_statement):
"""Returns an array of the values of the first column in a select:
select_values(ds, "SELECT id FROM companies LIMIT 3") => [1,2,3]
"""
values = []
poResultSet = self.ds.ExecuteSQL(sql_statement, None, None)
if poResultSet is not None:
poDefn = poResultSet.GetLayerDefn()
poFeature = poResultSet.GetNextFeature()
while poFeature is not None:
for iField in range(poDefn.GetFieldCount()):
values.append(poFeature.GetFieldAsString(iField))
poFeature = poResultSet.GetNextFeature()
self.ds.ReleaseResultSet(poResultSet)
return values
def table_exists(self, table):
exists = True
try:
self.ds.ExecuteSQL('SELECT 1 FROM %s' % table, None, None)
except:
exists = False
return exists
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