Editing layers¶
Deleting a field requires an instance of LayersUpdate or LayersWriter.
If these instances are not in the memory, the source will be overwritten.
LayersEditor instance¶
Writing layers¶
Creating a LayersSet with one layer in memory (RAM). The layer has neither coordinate system nor user defined fields.
from girs.feat.layers import LayersWriter
lrs = LayersWriter(SomeLayerName_0=[ogr.wkbPolygon], SomeLayerName_1=[ogr.wkbPolygon])
print lrs.get_description()
SomeLayerName
Creating a shapefile (one layer) without coordinate system and without user defined fields. This is not conform to ESRI ArcMap, which requires at least one user defined attribute.
lrs = LayersWriter('D:/tmp/some_shapefile.shp', layer_1=[ogr.wkbPolygon])
print lrs.get_description()
some_shapefile
Creating a shapefile without coordinate system and with two user defined fields.
fields = [FieldDefinition("Name", ogr.OFTString), FieldDefinition("Area", ogr.OFTReal)]
lrs = LayersWriter('D:/tmp/another_shapefile.shp', layer=[ogr.wkbPolygon, None, fields])
print lrs.get_field_names()
['Name', 'Area']
Creating a shapefile with coordinate system and with two user defined fields. See http://spatialreference.org/ for coordinate systems.
from osgeo import ogr
from girs.feat.layers import LayersWriter, FieldDefinition
from girs.srs import get_srs
fields = [FieldDefinition("Name", ogr.OFTString), FieldDefinition("Area", ogr.OFTReal)]
lrs = LayersWriter('D:/tmp/girs/studyarea.shp',
layer=[ogr.wkbPolygon, get_srs(epsg=4326), fields])
Inserting data into the layer passing a WKT geometry.
from girs.feat.geom import create_polygon
wkt = create_polygon([(6.77, 50.83), (7.16, 50.83), (7.16, 51.08),
(6.77, 51.08), (6.77, 50.83)]).ExportToWkt()
lrs.create_feature(geom=wkt, layer_number=0, Name=u'Köln', Area=0.0)
lrs.show()
geom Name Area
0 Polygon Köln 0.0
Inserting data into the layer passing an ogr geometry obtained from the utilities in girs.feat.geom.
from osgeo import ogr
from girs.feat.geom import create_polygon
from girs.feat.layers import LayersWriter, FieldDefinition
from girs.srs import get_srs
fields = [FieldDefinition("Name", ogr.OFTString), FieldDefinition("Area", ogr.OFTReal)]
lrs = LayersWriter('D:/tmp/girs/studyarea1.shp',
layer=[ogr.wkbPolygon, get_srs(epsg=4326), fields])
g = create_polygon([(6.77, 50.83), (7.16, 50.83), (7.16, 51.08), (6.77, 51.08), (6.77, 50.83)])
lrs.create_feature(geom=g, layer_number=0, Name=u'Düsseldorf', Area=10.0)
lrs.show()
geom Name Area
0 Polygon Düsseldorf 10.0
Creating a GML file with two layers:
from osgeo import ogr
from girs.feat.layers import LayersWriter, FieldDefinition
from girs.srs import get_srs
fields0 = [FieldDefinition("Name", ogr.OFTString), FieldDefinition("Area", ogr.OFTReal)]
fields1 = [FieldDefinition("Code", ogr.OFTInteger), FieldDefinition("Capital", ogr.OFTString)]
lrs = LayersWriter('D:/tmp/girs/studyarea.gml', 'GML',
name_0=[ogr.wkbPolygon, get_srs(epsg=4326), fields0],
name_1=[ogr.wkbPolygon, get_srs(epsg=4326), fields1])
print lrs.get_description(0), lrs.get_field_names(0)
print lrs.get_description(1), lrs.get_field_names(1)
Outputs:
name0 ['Name', 'Area']
name1 ['Code', 'Capital']
Update instance¶
from girs.feat.layers import LayersUpdate
lrs0 = LayersUpdate('D:/tmp/girs/DEU_adm_shp/DEU_adm4_copy.shp')
Delete fields¶
as in the example below:
from girs.feat.layers import LayersUpdate
lrs0 = LayersUpdate('D:/tmp/girs/DEU_adm_shp/DEU_adm4_copy.shp')
print 'Fields before:', lrs0.get_field_names()
lrs0.delete_fields(['ID_0', 'ISO', 'NAME_0', 'ID_1', 'ID_2', 'ID_3', 'ID_4',
'VARNAME_4', 'CCN_4', 'CCA_4', 'TYPE_4', 'ENGTYPE_4'])
print 'Fields after:', lrs0.get_field_names()
Output:
Fields before: ID_0, ISO, NAME_0, ID_1, NAME_1, ID_2, NAME_2, ID_3, NAME_3, ID_4, NAME_4, VARNAME_4, CCN_4, CCA_4, TYPE_4, ENGTYPE_4
Fields after: NAME_1, NAME_2, NAME_3, NAME_4
The original source can be copied before deleting fields:
from girs.feat.layers import LayersUpdate
lrs0 = LayersReader('D:/tmp/girs/DEU_adm_shp/DEU_adm4.shp').copy() # copy on memory
lrs0.delete_fields(['ID_0', 'ISO', 'NAME_0', 'ID_1', 'ID_2', 'ID_3', 'ID_4',
'VARNAME_4', 'CCN_4', 'CCA_4', 'TYPE_4', 'ENGTYPE_4'])
print 'Fields:', lrs0.get_field_names()
Calculating area¶
import ogr
from girs.feat.layers import FieldDefinition
lrs0 = LayersReader('D:/tmp/girs/DEU_adm_shp/DEU_adm4.shp')
lrs1 = lrs0.transform('D:/tmp/girs/DEU_adm_shp/DEU_adm4_copy.shp', epsg=32632)
fields_to_delete = lrs1.get_field_names()
fields_to_delete.remove('NAME_4')
lrs1.delete_fields(fields_to_delete)
lrs1.show(max_rows=4)
fields = [FieldDefinition(name='AREA', oft_type=ogr.OFTReal, width=18, precision=6)]
lrs1.add_fields(fields=fields)
lrs1.show(max_rows=4)
lrs1.calculate_area('AREA', scale=1.0 / 1000000.0)
lrs1.show(max_rows=4)
_GEOM_ NAME_4
FID
0 Polygon Allmendingen
1 Polygon Altheim
... ... ...
11300 Polygon Wohlsborn
11301 Polygon Weimar
[11302 rows x 2 columns]
_GEOM_ NAME_4 AREA
FID
0 Polygon Allmendingen NaN
1 Polygon Altheim NaN
... ... ... ...
11300 Polygon Wohlsborn NaN
11301 Polygon Weimar NaN
[11302 rows x 3 columns]
_GEOM_ NAME_4 AREA
FID
0 Polygon Allmendingen 46.050899
1 Polygon Altheim 7.711316
... ... ... ...
11300 Polygon Wohlsborn 4.077278
11301 Polygon Weimar 84.403305
[11302 rows x 3 columns]
Drivers¶
Drivers open a dataset to read, update, and create data. The driver short name can be explicitly given as parameter in functions or retrieved from file name extensions. The latter applies only for unambiguous file name extensions (suffixes).
Unambiguous suffix:
Suffix Drivers
0 000 S57
1 bna BNA
2 csv CSV
3 dat XPlane
4 dgn DGN
5 dxf DXF
6 e00 AVCE00
7 gdb OpenFileGDB
8 geojson GeoJSON
9 gml GML
10 gmt OGR_GMT
11 gpx GPX
12 gtm GPSTrackMaker
13 gtz GPSTrackMaker
14 gxt Geoconcept
15 jml JML
16 json GeoJSON
17 kml KML
18 map WAsP
19 mid MapInfo File
20 mif MapInfo File
21 nc netCDF
22 pix PCIDSK
23 rec REC
24 shp ESRI Shapefile
25 sql PGDUMP
26 svg SVG
27 sxf SXF
28 tab MapInfo File
29 thf EDIGEO
30 topojson GeoJSON
31 vct Idrisi
32 vrt OGR_VRT
33 x10 VDV
34 xml NAS
Ambiguous suffix:
Suffix Drivers
0 mdb PGeo, Geomedia
1 txt Geoconcept, VDV
Files without suffix:
DB2ODBC, UK .NTF, OGR_SDTS, Memory, ODBC, MSSQLSpatial, GeoRSS, GPSBabel, SUA, OpenAir, OGR_PDS,
HTF, AeronavFAA, ARCGEN, SEGUKOOA, SEGY, Walk, Selafin, TIGER, AVCBin
Driver are retrieved using FeatDrivers.get_driver(**kwargs). The parameters are any of drivername,
extension, or filename in this ranking order. drivername=None is interpreted as not
defined. If drivername is undefined, filename='' or filename=None requests a Memory driver.
print 1, FeatDrivers.get_driver().GetName()
print 2, FeatDrivers.get_driver(source='').GetName()
print 3, FeatDrivers.get_driver(source='some_source', drivername='Memory').GetName()
print 4, FeatDrivers.get_driver(source=None).GetName()
print 5, FeatDrivers.get_driver(source='a.gml').GetName()
print 6, FeatDrivers.get_driver(source='a.shp').GetName()
# print FeatDrivers.get_driver(source='a.mdb').GetName() # ERROR, since ambiguous
print 7, FeatDrivers.get_driver(source='a.mdb', drivername='Geomedia').GetName() # source='a.mdb' not used
1 Memory
2 Memory
3 Memory
4 Memory
5 GML
6 ESRI Shapefile
7 Geomedia