OGR and DXF files: Is it possible to handle layer names? (only “entities”)

Question

I'm using Python and OGR to extract the layers of a DXF file and convert them into SHP.

I began with:

import ogr, os, sys
driver = ogr.GetDriverByName('DXF')
datasource = driver.Open('test1.dxf', 0)
numberLayers = datasource.GetLayerCount()
for i in range(0, numberLayers):
    layer = datasource.GetLayerByIndex(i)
    layerName = layer.GetName()
    numberFeatures = layer.GetFeatureCount()
    print 'Layer=%s|Features=%s' % (layerName, numberFeatures)

but I get one only layer: entities (as expected: http://www.gdal.org/ogr/drv_dxf.html)

Obviously, it's the same information as if I execute: ogrinfo -so test1.dxf entities

My DXF file contains several CAD layers: "ROADS", "ELEVATION", ... Is it possible to handle these layer names with OGR? Thank you very much.

Answer 1

"Layer" is an just an attribute of the feature. But you can use OGR SQL and attribute filters:

import ogr

driver = ogr.GetDriverByName('DXF')
datasource = driver.Open('test1.dxf', 0)

layers=datasource.ExecuteSQL( "SELECT DISTINCT Layer FROM entities" )
layer=datasource.GetLayerByIndex(0)

for i in range(0, layers.GetFeatureCount()):
        layerName = layers.GetFeature(i).GetFieldAsString(0)
        layer.SetAttributeFilter( "Layer='%s'" % layerName)
        print 'Layer=%s|Features=%s' % (layerName, layer.GetFeatureCount())

Also works from the command line:

ogrinfo -sql "SELECT DISTINCT Layer FROM entities" test1.dxf

And:

ogrinfo -where "Layer='ROADS'" test1.dxf entities