Error trying to read a material shader node value in Python

I’m trying to use Python to read a value from a shader node in a material in Eevee in Blender 2.80.

I’ve got the full data path ‘[“Shader Nodetree”].nodes[“Mapping”].scale[2]’ from the tooltip:

but when I try to access that value in the Python console I get an error ‘key “Shader Nodetree” not found’:

So how do I access that node and its values in Python?

Eventually I stumbled over the answer.

The path to the Mapping node’s Z-scale value for my material (‘Volumetric Material’ in this case) is:[‘Volumetric.Material’].node_tree.nodes[‘Mapping’].scale[2]

Presumably the tooltip’s data path is irrelevant.