ArcPy (ArcMap): Modify Layer Symbology, Expanded

arcpy_arcmap_modify_layer_symbology_expanded.py

# Example 1a adapted from https://www.reddit.com/r/gis/comments/4rhvhh/map_automation_arcpymapping_make_lyr/
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# Reference: 1) http://desktop.arcgis.com/en/arcmap/latest/analyze/arcpy-mapping/layer-class.htm
#            2) https://docs.python.org/2/library/json.html

import arcpy
import json

lyr = # Layer object, typically from arcpy.mapping.ListLayers (arcpy._mapping.Layer)

# Example 1a: Modifying single-field renderer using undocumented _arc_object.renderer
new_field = # New field name for symbolizing layer
old_field = # Old field name for symbolizing layer 

sym_xml = lyr._arc_object.renderer
lyr._arc_object.renderer = sym_xml.replace(old_field, new_field)
arcpy.RefreshActiveView()

# Example 1b: Modifying single-field renderer using updateLayerFromJSON
new_field = # New field name for symbolizing layer (string)

sym_dict = json.loads(lyr._arc_object.getsymbology())
sym_dict["renderer"]["field1"] = new_field
lyr.updateLayerFromJSON(json.dumps({"drawingInfo": sym_dict}))
arcpy.RefreshActiveView()

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