Starting QGIS Desktop with Python script

Question

I looked at the QGIS official documentation (e.g., Using PyQGIS in custom applications) and a few questions here (e.g. Running QGIS through Python), but I was unable to find an example of a Python script that starts a regular QGIS app.

In other words, I look for the 'official'/recommended way to replicate the same results of running QGIS.exe (splash screen, main window visualization, etc.) using a qgis.py instead (i.e., without calling a QGIS executable using subprocess):

import logging
from qgis import core
logger = logging.getLogger(__name__)
def main():
 qgis_version = core.Qgis.version()
 logger.info('Running QGIS v.%s ...' % qgis_version)
 qg = core.QgsApplication([], True)
 qg.initQgis()
 # some code here that runs the QGIS splashscreen?
 # some code here that shows the QGIS main window?
 
 qg.exec_()
 qg.exitQgis()
 logger.info('Running QGIS v.%s ... DONE' % qgis_version)

(I am aware that it is possible to execute a startup.py, but this question is about writing a Python script that starts QGIS up.)

• Germán Carrillo: For reference, this is how a regular QGIS app is started. github.com/qgis/QGIS/blob/master/src/app/main.cpp It's not a trivial task to replicate.
• etrimaille: I don't think you can do it indeed, you need to replicate the file indeed main.cpp ...
• gmas80: I opened a related ticket on QGIS GitHub: github.com/qgis/QGIS/issues/45612
• Comrade Che: @gmas80 Out of curiosity, in what situation would it be useful?
• gmas80: @ComradeChe, for instance, to create a frozen version of a customized QGIS using PyInstaller.

Answer 1

You can use the pattern in the script:

from qgis import core
import subprocess
def main():
 qg = core.QgsApplication([], True)
 qg.initQgis()
 print("Starting QGIS")
 
 qgis_exe = r"C:\OSGeo4W64\bin\qgis-bin.exe"
 process = subprocess.Popen(qgis_exe, shell=True, stdout=subprocess.PIPE)
 process.wait()
 
 qg.exitQgis()
 print("QGIS is closed now")
main()

enter image description here

• gmas80: Thank you for the proposed solution. I am looking for a solution that does not call a .exe, but just replicating the results of calling qgis-bin.exe. I have modified my question. Hope that it is clearer now.