Select all nodes in Node Graph

from NatronGui import *
import NatronEngine

# select all nodes in the Node Graph #
app.selectAllNodes(app)

# in a list called 'currentNodes', we store the selected nodes #
currentNodes = app.getSelectedNodes()

# now we can cycle through all nodes to do whatever we want #
# a variable called 'node' is created on the fly #
# this variable will store the current node we are looking at in the list #
for node in currentNodes:
	do your stuff...