Exporting layout in standalone script with QGIS 3

Question

I'm trying to automate map export from a QGIS project in a standalone Python script, without interface.

Many of the scripts founds are for QGIS 2. For example the script written by @TimSutton here.

Here the code:

# coding=utf-8
# A simple demonstration of to generate a PDF using a QGIS project
# and a QGIS layout template.
#
# This code is public domain, use if for any purpose you see fit.
# Tim Sutton 2015
import sys
from qgis.core import (
 QgsProject, QgsComposition, QgsApplication, QgsProviderRegistry)
from qgis.gui import QgsMapCanvas, QgsLayerTreeMapCanvasBridge
from PyQt4.QtCore import QFileInfo
from PyQt4.QtXml import QDomDocument
gui_flag = True
app = QgsApplication(sys.argv, gui_flag)
# Make sure QGIS_PREFIX_PATH is set in your env if needed!
app.initQgis()
# Probably you want to tweak this
project_path = 'project.qgs'
# and this
template_path = 'template.qpt'
def make_pdf():
 canvas = QgsMapCanvas()
 # Load our project
 QgsProject.instance().read(QFileInfo(project_path))
 bridge = QgsLayerTreeMapCanvasBridge(
 QgsProject.instance().layerTreeRoot(), canvas)
 bridge.setCanvasLayers()
 template_file = file(template_path)
 template_content = template_file.read()
 template_file.close()
 document = QDomDocument()
 document.setContent(template_content)
 composition = QgsComposition(canvas.mapSettings())
 # You can use this to replace any string like this [key]
 # in the template with a new value. e.g. to replace
 # [date] pass a map like this {'date': '1 Jan 2012'}
 substitution_map = {
 'DATE_TIME_START': 'foo',
 'DATE_TIME_END': 'bar'}
 composition.loadFromTemplate(document, substitution_map)
 # You must set the id in the template
 map_item = composition.getComposerItemById('map')
 map_item.setMapCanvas(canvas)
 map_item.zoomToExtent(canvas.extent())
 # You must set the id in the template
 legend_item = composition.getComposerItemById('legend')
 legend_item.updateLegend()
 composition.refreshItems()
 composition.exportAsPDF('report.pdf')
 QgsProject.instance().clear()
make_pdf()

QGIS 3 is now based on Python 3 and Qt 5 and I try to simply export a layout with a script without load / show the QGIS GUI.

Which script to use under QGIS 3?

Answer 1

Here is the solution working for me. The python file must be in the same directory as the QGIS 3 project file :

#!/usr/bin/env python3
import os
from qgis.core import (QgsProject, QgsLayoutExporter, QgsApplication)
QgsApplication.setPrefixPath("/usr", True)
gui_flag = False
app = QgsApplication([], gui_flag)
app.initQgis()
project_path = os.getcwd() + '/project.qgz'
project_instance = QgsProject.instance()
project_instance.setFileName(project_path)
project_instance.read()
manager = QgsProject.instance().layoutManager()
layout = manager.layoutByName("my_layout") # name of the layout
# or layout = manager.layouts()[0] # first layout
exporter = QgsLayoutExporter(layout)
exporter.exportToPdf(project_instance.absolutePath() + "/layout.pdf",
 QgsLayoutExporter.PdfExportSettings())
app.exitQgis()

• Inactivated Account: worked for me once the / was included in the qgis project file location and the output directory. Thanks!
• Newton Monteiro: Through this method is possible export an ATLAS with individual maps?
• J. Monticolo: Yes, you can look at this answer : gis.stackexchange.com/a/328168/93097