QGIS 3 PyQGIS Script - Merge Layers and Export to csv with KML geom field

Question

I previously had a script in 2.18 that exported csv files with kml geometry's file by file. I'm now wanting to move to QGIS 3 and do the same process except Merge the point layers then add the geometry field then export to csv

This is my 2.18 script - it does not preform the merging but does everything else I am after

import os, processing,ogr,csv,sys
from qgis.core import QgsMapLayerRegistry
from qgis.utils import iface
crs = 'EPSG:4326' 
#shapefiles = QgsMapLayerRegistry.instance().mapLayers().values() #All Map Layers
shapefiles = QgsMapLayerRegistry.instance().mapLayers()
shapefiles = iface.legendInterface().selectedLayers()
shapefiles = iface.legendInterface().layers()
excludeshapes1 = 'copy'
excludeshapes2 = 'parcel'
excludeshapes3 = 'contour'
excludeshapes4 = 'road'
excludeshapes5 = 'address'
for shapes in shapefiles:
 sname =shapes.name().lower()
 print sname 
 print "Shape Type"
 print shapes.type()
 if excludeshapes1 not in sname and excludeshapes2 not in sname and excludeshapes3 not in sname and excludeshapes4 not in sname and excludeshapes5 not in sname:
 if shapes.type() == 0:
 print "WKB Type"
 print shapes.wkbType() 
 #print shapes.name()
 sname =shapes.name()
 #print sname 
 #print shapes.type() == QgsMapLayer.VectorLayer
 if shapes.type() == 0:
 if shapes.wkbType() ==0:
 print " WKBUnknown" 
 elif shapes.wkbType() == 100:
 print " No Geom" 
 elif shapes.wkbType() == 1 or shapes.wkbType() == 4:
 print " Point" 
 try:
 myfilepath = shapes.dataProvider().dataSourceUri()
 (myDirectory,nameFile) = os.path.split(myfilepath)
 csvfile= myDirectory + "/" + "WGS84_Point" + shapes.name()+".csv"
 processing.runalg("qgis:reprojectlayer", shapes, crs, myDirectory + "/" + "WGS84_Point" + shapes.name())
 #Open files
 daShapefile = myDirectory+"/" + "WGS84_Point"+shapes.name()+".shp"
 driver = ogr.GetDriverByName('ESRI Shapefile')
 dataSource = driver.Open(daShapefile, 0) # 0 means read-only. 1 means writeable.
 csvfile=open(csvfile,'wb')
 ds=ogr.Open(daShapefile)
 lyr=ds.GetLayer()
 #Get field names
 dfn=lyr.GetLayerDefn()
 nfields=dfn.GetFieldCount()
 fields=[]
 for i in range(nfields):
 fields.append(dfn.GetFieldDefn(i).GetName())
 fields.append('kmlgeometry')
 csvwriter = csv.DictWriter(csvfile, fields)
 try:csvwriter.writeheader() #python 2.7+
 except:csvfile.write(','.join(fields)+'\n')
 # Write attributes and kml out to csv
 for feat in lyr:
 if feat.GetGeometryRef() is None:
 print("No Valid Geometry" )
 else:
 attributes=feat.items()
 geom=feat.GetGeometryRef()
 attributes['kmlgeometry']=geom.ExportToKML()
 csvwriter.writerow(attributes)
 #clean up
 del csvwriter,lyr,ds
 csvfile.close()
 except:
 pass
 elif shapes.wkbType() == 2 or shapes.wkbType() == 5 :
 print " Line" 
 try:
 myfilepath = shapes.dataProvider().dataSourceUri()
 (myDirectory,nameFile) = os.path.split(myfilepath)
 csvfile= myDirectory + "/" + "WGS84_Line" + shapes.name()+".csv"
 processing.runalg("qgis:reprojectlayer", shapes, crs, myDirectory + "/" + "WGS84_Line" + shapes.name())
 #Open files
 daShapefile = myDirectory+"/" + "WGS84_Line"+shapes.name()+".shp"
 driver = ogr.GetDriverByName('ESRI Shapefile')
 dataSource = driver.Open(daShapefile, 0) # 0 means read-only. 1 means writeable.
 csvfile=open(csvfile,'wb')
 ds=ogr.Open(daShapefile)
 lyr=ds.GetLayer()
 #Get field names
 dfn=lyr.GetLayerDefn()
 nfields=dfn.GetFieldCount()
 fields=[]
 for i in range(nfields):
 fields.append(dfn.GetFieldDefn(i).GetName())
 fields.append('kmlgeometry')
 csvwriter = csv.DictWriter(csvfile, fields)
 try:csvwriter.writeheader() #python 2.7+
 except:csvfile.write(','.join(fields)+'\n')
 # Write attributes and kml out to csv
 for feat in lyr:
 if feat.GetGeometryRef() is None:
 print("No Valid Geometry" )
 else:
 attributes=feat.items()
 geom=feat.GetGeometryRef()
 attributes['kmlgeometry']=geom.ExportToKML()
 csvwriter.writerow(attributes)
 #clean up
 del csvwriter,lyr,ds
 csvfile.close()
 except:
 pass
 elif shapes.wkbType() == 3 or shapes.wkbType() == 6: 
 print " Polygon" 
 try:
 myfilepath = shapes.dataProvider().dataSourceUri()
 (myDirectory,nameFile) = os.path.split(myfilepath)
 csvfile= myDirectory + "/" + "WGS84_Polygon" + shapes.name()+".csv"
 processing.runalg("qgis:reprojectlayer", shapes, crs, myDirectory + "/" + "WGS84_Polygon" + shapes.name())
 #Open files
 daShapefile = myDirectory+"/" + "WGS84_Polygon"+shapes.name()+".shp"
 driver = ogr.GetDriverByName('ESRI Shapefile')
 dataSource = driver.Open(daShapefile, 0) # 0 means read-only. 1 means writeable.
 csvfile=open(csvfile,'wb')
 ds=ogr.Open(daShapefile)
 lyr=ds.GetLayer()
 #Get field names
 dfn=lyr.GetLayerDefn()
 nfields=dfn.GetFieldCount()
 fields=[]
 for i in range(nfields):
 fields.append(dfn.GetFieldDefn(i).GetName())
 fields.append('kmlgeometry')
 csvwriter = csv.DictWriter(csvfile, fields)
 try:csvwriter.writeheader() #python 2.7+
 except:csvfile.write(','.join(fields)+'\n')
 # Write attributes and kml out to csv
 for feat in lyr:
 if feat.GetGeometryRef() is None:
 print("No Valid Geometry" )
 else:
 attributes=feat.items()
 geom=feat.GetGeometryRef()
 attributes['kmlgeometry']=geom.ExportToKML()
 csvwriter.writerow(attributes)
 #clean up
 del csvwriter,lyr,ds
 csvfile.close()
 except:
 pass
 elif shapes.wkbType() < 0 or shapes.wkbType() > 6:
 try:
 print ("Not Processed Layer: ") + sname
 print ("Not Processed-WKBType: ") + shapes.wkbType() 
 except:
 pass
 else:
 print sname
 raise Exception('Should never happen')

I know there are options avaible in QGIS3 like mergevetorlayers and reprojectlayer.

Answer 1

there are some changes in the Qgis Python API (see https://qgis.org/api/api_break.html), for example QgsMapLayerRegistry does not exist anymore. Change the first lines into:

group =QgsProject.instance().layerTreeRoot().children()
shapefiles = [ item.layer() for item in group ] #list of all layers