Saving temporary layer to shapefile using PyQGIS

Question

I'm attempting to save a polygon created in a scratch layer to a shapefile. The Python code below is a simplified example. Note the questions: Saving layer as shapefile using PyQGIS and Setting QgsVectorFileWriter.SaveVectorOptions for QGIS 3 provided some of the help, which I'm including in this post for future reference,

# Attach libraries
from qgis.core import * # attach main QGIS library
from qgis.utils import * # attach main python library
import os # attach operating system library

# Set the working directory
wd = "C:/test" # Set work directory
os.chdir(wd) # Change the directory

# Set a variable for the current project instance
  Prj = QgsProject().instance() # Object for current project

# Save the project to this file name
pnm = "Test.qgs" # Project file name
pnm = wd + "/" + pnm # Concat. with path
Prj.write(pnm) # Save the project

# Create an array [] object with the polygon vertices
vrtcs = []
vrtcs.append(QgsPointXY(396100,8969000))
vrtcs.append(QgsPointXY(396100,8973900))
vrtcs.append(QgsPointXY(397900,8973900))
vrtcs.append(QgsPointXY(397900,8969000))

# Create a polygon from the vertices
ply_01 = QgsGeometry.fromPolygonXY([vrtcs])

# Create a feature object then append the polygon into 
ftr = QgsFeature()
ftr.setGeometry(ply_01)
print(ftr.geometry())

# Create a layer for the feature and add to the project
lyr = QgsVectorLayer('Polygon?crs=epsg:29194','Test',"memory")
Prj.addMapLayers([lyr])

# Make the layer editable, add the feature and save
lyr.startEditing()
lyr.addFeature(ftr)
lyr.commitChanges()

# Save as a shapefile
Fl_ou = 'Test.shp'
Fl_ou = wd + '/' + Fl_ou
writer = QgsVectorFileWriter(lry, Fl_ou,'urf-8','ESRI Shapefile')

When I execute the last line I get the following error "NameError: name 'lry' is not defined".

However, when I enter type(lyr) into the console it recognizes the variable lyr as a <class 'qgis._core.QgsVectorLayer'> so I am unsure why I'm getting the not defined error.

Answer 1

Use writeAsVectorFormatV2 method of QgsVectorFileWriter class.

# Attach libraries
from qgis.core import * # attach main QGIS library
from qgis.utils import * # attach main python library
import os # attach operating system library

# Set the working directory
wd = "C:/test" # Set work directory
os.chdir(wd) # Change the directory

# Set a variable for the current project instance
Prj = QgsProject().instance() # Object for current project

# Save the project to this file name
pnm = "Test.qgs" # Project file name
pnm = wd + "/" + pnm # Concat. with path
Prj.write(pnm) # Save the project

# Create an array [] object with the polygon vertices
vrtcs = []
vrtcs.append(QgsPointXY(396100,8969000))
vrtcs.append(QgsPointXY(396100,8973900))
vrtcs.append(QgsPointXY(397900,8973900))
vrtcs.append(QgsPointXY(397900,8969000))

# Create a polygon from the vertices
ply_01 = QgsGeometry.fromPolygonXY([vrtcs])

# Create a feature object then append the polygon into 
ftr = QgsFeature()
ftr.setGeometry(ply_01)
print(ftr.geometry())

# Create a layer for the feature and add to the project
lyr = QgsVectorLayer('Polygon?crs=epsg:29194','Test',"memory")
Prj.addMapLayers([lyr])

# Make the layer editable, add the feature and save
lyr.startEditing()
lyr.addFeature(ftr)
lyr.commitChanges()

# Save as a shapefile
Fl_ou = 'Test.shp'
Fl_ou = wd + '/' + Fl_ou

options = QgsVectorFileWriter.SaveVectorOptions()
options.driverName = "ESRI Shapefile"

QgsVectorFileWriter.writeAsVectorFormatV2(lyr, Fl_ou, QgsCoordinateTransformContext(), options)

Answer 2

I understand this is an old post, but I developed a plugin that saves all vector layers as .gpkg. All temporary layers are automatically made permanent. Want to share if it can be of use: https://plugins.qgis.org/plugins/SaveAllScript/