How to rename unique value using arcpy

Question

I work with several MXD files. In each map there a polygon layer with unique values:

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I try to change in the table of contents the "a" into "land use" by using this code:

import arcpy,os,sys
from arcpy import env
env.workspace = r"G:\desktop\Project"
for mxdname in arcpy.ListFiles("*.mxd"):
 print mxdname 
 mxd = arcpy.mapping.MapDocument(r"G:\desktop\Project\\" + mxdname)
 df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0] 
 lyr = arcpy.mapping.ListLayers(mxd, "*")[0]
 if lyr.symbologyType == "UNIQUE_VALUES":
 vals = lyr.symbology.classLabels
 for v in vals:
 if v == "a":
 print lyr.name
 v = 'landUse'
 print v 
 mxd.save()
del mxd 

I just want to change the name in the table of content, and not change the attribute table value. When running this code i get this result and with no change in the maps:

>>> 
project.mxd
polygon
landUse
>>> 

Answer 1

To update the labels, you'll need to update them all at once by providing a list to lyr.symbology.classLabels.

if lyr.symbologyType == "UNIQUE_VALUES":
 vals = lyr.symbology.classLabels
 newLabels = []
 for v in vals:
 if v == "a":
 v = 'landUse'
 newLabels.append(v) # push each label into the list
 lyr.symbology.classLabels = newLabels # apply the new labels
mxd.save()