Help! Graduated Colors Symbology Automation and Classification

Question

Does anyone know how to apply the graduated colors symbology using ArcPy?

I will use manual classification and apply percentages rather than values. For each map i make, i need to represent 1%, 5%, 50%, 75% ranges of the max value in the data. The problem starts when I import symbology from a layer. I can import the symbology and labels, but the percentage ranges represent the previous data.

Can i set the classification to represent these percentages using ArcPy?

Thanks!!

ShaneArmour · Answer

Thank you!!!!

I am working on the automation now. I'll let you know if it works.

ArkadiuszMatoszka · Answer

Use cursor to extract max value then after importing symbology from .lyr use symbology attribute of layer, and set classBreakValues parameter (it should be sorted list of break values). So it should looks something like:
...

with arcpy.da.SearchCursor(lyr, (field_name)) as cur:
  max_v = max([v[0] for v in cur])
...
if lyr.supports('SYMBOLOGY'):
  lyr.symbology.valueField = field_name
  lyr.symbology.classBreakValues = [0, 0.01 * max_v, 0.05 * max_v, 0.5 * max_v, 0.75 *max_v, max_v]
  
...
arcpy.RefreshActiveView()

Regards,
Arek

ArkadiuszMatoszka · Answer

After importing symbology from .lyr use symbology attribute of layer, and set classBreakValues parameter (it should be sorted list of break values). So it should look like:
...
lyr = arcpy.mapping.ListLayers(mxd, 'layer_name_in_mxd)[0]
if lyr.supports('SYMBOLOGY'):
  lyr.symbology.valueField = field_name
  lyr.symbology.classBreakValues = [0, 0.01, 0.05, 0.5, 0.75, 1]
  lyr.symbology.classBreakLabels = ['<1%', '1-5%', '5-50%', '50-75%', '>75%']
...
arcpy.RefreshActiveView()

Regards.
Arek