Attempting to run first script after setting up environment for QGIS and python?

Question

I uninstalled arcmap and all existing python installations. Then I followed the instructions from https://www.youtube.com/watch?v=Chq9fTRKsHk&t=2s to install qgis and set the environment variables.

I'm attempting to run the script from the second video (https://www.youtube.com/watch?v=Y8JjvBKOCDk&list=PLzHdTn7Pdxs4AvkJeJwlyav2-at9QwKWR) which should launch a blank canvas.

from qgis.core import *
from qgis.gui import *
from PyQt4.QtCore import *
from PyQt4 import QtGui

app = QtGui.QApplication

QgsApplication.setPrefixPath("C:/OSGeo4W/apps/qgis", True)
QgsApplication.initQgis()

window = QtGui.QMainWindow()
window_frame = QtGui.QFrame(window) 11
window.setCentralWidget(window_frame)
frame_layout = QtGui.QGridLayout(window_frame)

canvas = QgsMapCanvas()
frame_layout.addWidget(canvas)

window.show()
app.exec_()

It's supposed to bring up a canvas but does not.

The error I'm getting is

Process finished with exit code -1073741819 (0xC0000005)

I don't know if the problem is in the environment variables or in the script. Any ideas?

Answer 1

Try editing your code with the following:

• Replace app = QtGui.QApplication with app = QApplication([], True)
• Move the above line after you have set your prefix path.
• Add from PyQt4.QtGui import QApplication when importing PyQt4 modules
• Remove 11 in the line window_frame = QtGui.QFrame(window) 11

---

Running the above works for me, here is the code I used:

from qgis.core import *
from qgis.gui import *
from PyQt4.QtCore import *
from PyQt4 import QtGui
from PyQt4.QtGui import QApplication

QgsApplication.setPrefixPath("C:/OSGeo4W/apps/qgis", True)
app = QApplication([], True)
QgsApplication.initQgis()

window = QtGui.QMainWindow()
window_frame = QtGui.QFrame(window)
window.setCentralWidget(window_frame)
frame_layout = QtGui.QGridLayout(window_frame)

canvas = QgsMapCanvas()
frame_layout.addWidget(canvas)

window.show()
app.exec_()