QGIS Map tools and Map canvas giving QString errors

Question

I'm trying to learn more about using QGIS Map Canvas widgets and creating custom map tools, so the information from the PyQGIS cookbook is very helpful. After trying to experiment with mywnd.py from this page: https://www.qgis.org/en/docs/pyqgis_developer_cookbook/canvas.html I had a few difficulties.

On first try running the script, I got ImportError: cannot import name QString. To overcome this error I imported like so:

try:
    from PyQt4.QtCore import SIGNAL, Qt, QString
except ImportError:
    QString = str

That allowed me to get through the import. However, after inputting the following lines into the python console as directed by the cookbook, I got NameError: global name 'QString' is not defined

w = mywnd.MyWnd(qgis.utils.iface.activeLayer())

Answer 1

That documentation in the cookbook is a little out of date. You shouldn't need to use QString at all now, and the following code should work:

actionZoomIn = QAction("Zoom in", self)
actionZoomOut = QAction("Zoom out", self)
actionPan = QAction("Pan", self)

Basically, just remove all references to QString - they'll be converted automatically behind the scenes and you don't need to do it manually yourself anymore.