Define pen width of a Line layer in PyQGIS

Question

I have created a line shapefile layer (memory layer) created in Python Console of QGIS. Now I want to define the thickness of the line features that are being created. I am aware of the method by which the line styles/symbology can be imported from the existing '.qml' file.

self.setLayerSymbology(vlayer, "Parent_PermanentMarks.qml") 

Is there any way by which symbology (line thickness) of the lines can be defined 'on the go' via python console?

Answer 1

The below script worked for me.

from qgis.utils import iface
from qgis.core import *
from qgis.utils import *
from qgis.gui import *

vlayer = QgsVectorLayer("C:\SampleData\world_borders_lines.shp", "world_borders", "ogr")
props = { 'width' : '2', 'color' : '0,0,255' }
sl = QgsSymbolLayerV2Registry.instance().symbolLayerMetadata("SimpleLine").createSymbolLayer(props)
s = QgsLineSymbolV2([sl])
vlayer.setRendererV2( QgsSingleSymbolRendererV2( s ) )
QgsMapLayerRegistry.instance().addMapLayer(vlayer)

Answer 2

Pen width (only line width, not other parameters such as line color) can be set using

symbol.setWidth()

Full code (Set Line width for the line shapefile layer being loaded):

vlayer = QgsVectorLayer("D:\\abs\\path\\Lines.shp", "LineLayer", "ogr")        
symbols = vlayer.rendererV2().symbols()
symbol = symbols[0]
symbol.setWidth(0.46)
QgsMapLayerRegistry.instance().addMapLayer(vlayer)

NB: To change line color along with pen width, check out the other answer to this question.