How can I change the conductivity of a material using the Python API

edit

You can try something like

import openstudio

m = openstudio.model.Model()
material = openstudio.model.StandardOpaqueMaterial(m)
original_conductivity = material.thermalConductivity()
material.setThermalConductivity(0.2)

print ("The original conductivity was"+" "+str(original_conductivity)+" and the new conductivity is "+str(material.thermalConductivity()))

The original conductivity was 0.1 and the new conductivity is 0.2

Replace the material object with the object you want to change.