Accessing iface in QGIS from Jupyter Notebook?

Question

I am trying to work with an active QGIS from a jupyter notebook - specifically I'd like to be able to access iface so I can perform some layer calculations.

I am having trouble getting the map layers and working with the iface.

from qgis.core import *
import qgis.utils
from qgis.utils import iface, plugins

import numpy
import pandas
import pathlib, os, sys

 
project_name= r"C:\path-to-project.qgz"
app= QgsApplication([], False)
QgsApplication.setPrefixPath(r"C:\OSGeo4W\apps\qgis", True)
QgsApplication.initQgis() 

current_project= QgsProject.instance()
current_project.setFileName(project_name)
print(current_project) #this prints a project instance

print(current_project.mapLayers()) #this returns an empty dictionary {}

layer = iface.activeLayer() #this gives an error: NoneType has no method activeLayer

layers = iface.mapCanvas().layers() #same error as above: it thinks iface is None

For some reason it is not able to use iface and gives me a NoneType error.

How do I work with the currently running QGIS instance from a jupyter notebook and have access to the map layers?

Answer 1

My question was similar to Listing project layers in standalone PyQGIS script.

What ended up working was:

from qgis.core import *    
from PyQt5.QtCore import QFileInfo    
import os
from PyQt5 import QtCore, QtGui, QtWidgets
from os.path import expanduser
from qgis.core import QgsApplication

home = expanduser("~")
QgsApplication( [], False, home + "/AppData/Local/Temp" )
QgsApplication.setPrefixPath("C:/OSGeo4W64/apps/qgis", True)
app = QtWidgets.QApplication([])

QgsApplication.initQgis()

fname = r"C:\path-to-project.qgz"
# Get the project instance
project = QgsProject.instance()
# Open the project
project.read(fname)
print(project.fileName())

map_layers = QgsProject.instance().mapLayers().values()
print(map_layers) #this now has the layers in a dictionary