Adding Layers to a opened Qgis project via Python IDLE

Question

I have a project opened in Qgis "qgis_training.qgs" and I am trying to add a layer to it via python2.7.6 IDLE using the following code:

from qgis.core import *
from qgis.utils import iface
from PyQt4.QtCore import QFileInfo


# Get the project instance
project = QgsProject.instance()
# Print the current project file name (might be empty in case no projects have been loaded)
print project.fileName()

# Load another project
project.read(QFileInfo('/home/julierme/Desktop/qgis/projetos/qgis_training.qgs'))
print project.fileName()

bridge = QgsLayerTreeMapCanvasBridge( \
QgsProject.instance().layerTreeRoot(), canvas)

# Now you can safely load your project and see it in the canvas
project.read(QFileInfo('/home/julierme/Desktop/qgis/projetos/qgis_training.qgs'))


# Function addVectorLayer: Open and display a vector layer in QGIS  
layer = iface.addVectorLayer("/home/julierme/Desktop/amazonia_sar/amapa/SHP/mask_covmingrad.shp", "mask_covmingrad", "ogr")
if not layer.IsValid():
    print "Layer failed to load!"

# Save the project to the same
project.write()   

I am getting the error message below while running it:

Traceback (most recent call last):
  File "/home/julierme/pyqgis/scripts/script2.py", line 17, in <module>
    bridge = QgsLayerTreeMapCanvasBridge( \
NameError: name 'QgsLayerTreeMapCanvasBridge' is not defined

How can I solve this issue and achieve my goal?

Answer 1

QgsLayerTreeMapCanvasBridge is in the gui module so you need to:

from qgis.gui import QgsLayerTreeMapCanvasBridge