I would like to change the zoom factor of QGIS dynamically without restarting QGIS. The changed settings I would like to use for a plugin would be that it let's me dynamically change the zoom behaviour when I use the mouse wheel for zooming in and out.

I know that I can change the QGIS-Settings like that:

from PyQt4.QtCore import QSettings
s = QSettings() #getting qgis settings
s.setValue("/Qgis/zoom_factor", 1.1)

But this requires a restart of QGIS to really change the zoom behaviour. Is there anything else I could do to make QGIS accept the new settings like it does when I click the "OK"-button in the settings dialog?


There is no need to alter settings, you can change the zoom factor for the current QGIS session.

For QGIS <= v2.18 (see Wheel actions enum):

zoomFactor = 3
iface.mapCanvas().setWheelAction( 0, zoomFactor ) # Wheel action, Zoom factor

For upcoming QGIS 3, there is a new method (wheel actions have been removed):

zoomFactor = 3
iface.mapCanvas().setWheelFactor( zoomFactor )
  • 2
    Or use QgsMapCanvas.WheelZoom instead of 0 to make it a bit better readable. Karma points for mentioning the QGIS 3.0 API. Jan 12 '17 at 15:08
  • This can be also used to switch mouse wheel behavior to "ArcMap" style by setting zoomFactor to below 1, for example: iface.mapCanvas().setWheelFactor( 0.5 )
    – Miro
    Jul 26 '19 at 3:00
  • Also be aware iface.mapCanvas().setWheelFactor() changes all zoom in / zoom out functionality (tools), not only mouse wheel behavior.
    – Miro
    Jul 26 '19 at 3:19

If you are looking for zoom functions, they are defined in the QgsMapCanvas Class. For example, in your case it could be used something like this:

canvas = qgis.utils.iface.mapCanvas()

If I run this code from the Python Console, it zooms the canvas by a factor of 1.1. Does it work for you?

  • thanks but I still want use the mouse wheel for zooming. I just want to dynamically adjust how much it zooms in or out when I use the mousewheel Jan 12 '17 at 14:28
  • Sorry, I was distracted. I'm glad you solved your problem.
    – mgri
    Jan 12 '17 at 14:43

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