Assigning function to a key in QGIS Plugin

Question

I have trouble assigning function to a hotkey in my plugin. I have a class that does things with a mouse click. I'd like to assign another function to a keyboard key or sequence. I've tried two different approaches:

1. https://docs.qgis.org/testing/en/docs/pyqgis_developer_cookbook/snippets.html#how-to-call-a-method-by-a-key-shortcut This assigns given key sequence as a shortcut, but does nothing.

2. def scale():
       iface.mapCanvas.zoomScale( 2500 )
   
   shortcut = QShortcut(QKeySequence(Qt.ControlModifier + Qt.Key_Q), iface.mainWindow())
   shortcut.setContext(Qt.ApplicationShortcut)
   shortcut.activated.connect(scale)
   

Both don't return any errors, but just doesn't work. I made sure that key sequences aren't in use. What am I missing?

Answer 1

Manually, I tried out your sequence placed at second code, Ctrl+Q, and it is assigned for quitting QGIS; as it can be observed at following image:

So, I modified slightly your code:

from PyQt4.QtCore import *
from PyQt4.QtGui import QShortcut, QKeySequence

def scale():
    iface.mapCanvas().zoomScale( 2500 )
    print "Hello"

shortcut = QShortcut(QKeySequence(Qt.ControlModifier + Qt.Key_F3), iface.mainWindow())
shortcut.setContext(Qt.ApplicationShortcut)
shortcut.activated.connect(scale)

for also printing "Hello" at Python Console and to assing Qt.Key_F3 to Qt.ControlModifier.

After running it at Python Console of QGIS, keyboard Ctrl + F3 sequence resulted as expected (following image). It was printed "Hello" at Python Console and scale was changed to 2500 (see red rectangles).