fn = 'D:/PHD/výučba/Python/cvičenia/dmr100m.tif'
rlayer = iface.addRasterLayer(fn, 'DMR_farebny')
stats = rlayer.dataProvider().bandStatistics(1, QgsRasterBandStats.All)
min = stats.minimumValue
max = stats.maximumValue
fnc = QgsColorRampShader()
fnc.setColorRampType(QgsColorRampShader.Interpolated)
lst = [QgsColorRampShader.ColorRampItem(min, QColor(0,0,0)),\
  QgsColorRampShader.ColorRampItem(max, QColor(255,255,255))]
fnc.setColorRampItemList(lst)
shader = QgsRasterShader()
shader.setRasterShaderFunction(fnc)
renderer = QgsSingleBandPseudoColorRenderer(rlayer.dataProvider(), 1, shader)
rlayer.setRenderer(renderer)