"AttributeError: 'QgisInterface' object has no attribute 'legendInterface'" in PyQGIS 3

Question

The following piece of code works well in QGIS 2, however, it does not work in QGIS 3.

myDir = 'd:/work/output_folder/'

layers = iface.legendInterface().layers()
pipe = QgsRasterPipe()

for layer in layers:
   extent = layer.extent()
   width, height = layer.width(), layer.height()
   renderer = layer.renderer()
   provider = layer.dataProvider()
   crs = layer.crs().toWkt() 
   pipe.set(provider.clone())
   pipe.set(renderer.clone())
   opts = ["COMPRESS=LZW"] 
   file_writer = QgsRasterFileWriter(myDir + layer.name() + ".tif")
   file_writer.setCreateOptions(opts)
   file_writer.writeRaster(pipe, width, height, extent, layer.crs())

This is the error I get when I run the code:

Traceback (most recent call last):
  File "C:\PROGRA~1\QGIS3~1.0\apps\Python36\lib\code.py", line 91, in runcode
    exec(code, self.locals)
  File "<input>", line 1, in <module>
AttributeError: 'QgisInterface' object has no attribute 'legendInterface'

Does someone know what has replaced legendInterface in the new version or what other changes I might have to make to get this to run in QGIS 3?

Answer 1

You could just replace

layers = iface.legendInterface().layers()

with

layers = [layer for layer in QgsProject.instance().mapLayers().values()]

Answer 2

The equivalent of

layers = self.iface.legendInterface().layers()

in QGIS 3 is

layers = [tree_layer.layer() for tree_layer in QgsProject.instance().layerTreeRoot().findLayers()]

This recursively finds all layers and returns them in the same order as listed in Layers Panel.

Answer 3

I found this to list layers:

layers = qgis.core.QgsProject.instance().layerTreeRoot().layerOrder()

Answer 4

Have a look at https://qgis.org/api/api_break.html - there are literally thousands of changes to the API, which scripts need to be upgraded to handle.

QgsLegendInterface was removed. It was replaced by layer tree API (QgsLayerTreeNode class and others). Methods that deal with custom actions in main window's layer tree context menu were moved to QgisInterface:

• addLegendLayerAction() moved to QgisInterface::addCustomActionForLayerType()
• addLegendLayerActionForLayer() moved to QgisInterface::addCustomActionForLayer()
• removeLegendLayerAction() moved to QgisInterface::removeCustomActionForLayerType()