How to reverse the color scheme for a preset color ramp using ArcPy inside of ArcGIS Pro (by changing the class breaks)

Question

I have a Jupyter Notebook in my ArcGIS Pro project which changes the symbology of my map layer. In this script I manually set the class breaks using the classBreakValues variable which works as long as the list starts from the lowest number (3) to the highest (15). Example below:

from datetime import datetime # for obtaining today's date
import os

# set up project and map
p = arcpy.mp.ArcGISProject('CURRENT')
m = p.listMaps('Map')[0]
lyr = m.listLayers('PHUC4s_joinedData')[0]
Layout = p.listLayouts('Layout')[0]

# create a list of fields
fields = arcpy.ListFields(lyr) # creates a list of fields

# create the outputs
sym.updateRenderer('SimpleRenderer') # reset renderer
sym.updateRenderer('GraduatedColorsRenderer')
sym.renderer.classificationField = 'complete_data.csv.Ind_RegRank_pctRank'
sym.renderer.breakCount = 4
sym.renderer.colorRamp = p.listColorRamps('Oranges (Continuous)')[0]

## general change for most legends
classBreakValues = [3, 7, 10, 15]
classBreakLabels = ['3', '7', '10', '15']
label_loop_count = 0                            
for brk in sym.renderer.classBreaks:
    brk.upperBound = classBreakValues[label_loop_count]
    brk.label = classBreakLabels[label_loop_count]
    label_loop_count += 1 

# save symbology back into the layer
lyr.symbology = sym

Now the issue is that I want to reverse the color scheme so that the lowest numbers are the darkest. I tried to change classBreakValues to [15, 10, 7, 3] to reverse the color order but the outcome is just a single-colored map set to whatever color is set to 15.

This map is an example output from the code I posted above. Here I have classBreakValues = [3, 7, 10, 15]. If I try to reverse the colors with classBreakValues = [15, 10, 7, 3] I end up with a map only filled with that white color. My ultimate goal is to just reverse the color order.

Answer 1

There doesn't seem to be a one-liner to reverse the color scheme, but I was able to do so by looking at the RGB values for a color scheme in ArcGIS Pro and manually plugging them in for "brk.symbol.color".

#imports
from datetime import datetime # for obtaining today's date
import os

# set up project and map
p = arcpy.mp.ArcGISProject('CURRENT')
m = p.listMaps('Map')[0]
lyr = m.listLayers('PHUC4s_joinedData')[0]
Layout = p.listLayouts('Layout')[0]

# create a list of fields
fields = arcpy.ListFields(lyr) # creates a list of fields

# create the outputs
sym = lyr.symbology
sym.updateRenderer('SimpleRenderer') # reset renderer
sym.updateRenderer('GraduatedColorsRenderer')
sym.renderer.classificationField = 'complete_data.csv.Ind_RegRank_pctRank'
sym.renderer.breakCount = 4


## general change for most legends
classBreakValues = [3, 7, 10, 15]
classBreakLabels = ['3', '7', '10', '15']
classBreakColorOrange = [{'RGB' : [127, 39, 4, 100]},
                         {'RGB' : [233, 94, 13, 100]},
                         {'RGB' : [253, 185, 125, 100]},
                         {'RGB' : [255, 245, 235, 100]}                         
                        ]

label_loop_count = 0                            
for brk in sym.renderer.classBreaks:
    brk.upperBound = classBreakValues[label_loop_count]
    brk.label = classBreakLabels[label_loop_count]
    brk.symbol.color = classBreakColorOrange[label_loop_count]
    label_loop_count += 1 

# save symbology back into the layer
lyr.symbology = sym

This created a map where the low numbers are dark and high numbers are lighter...shown below: