How to remove a specific unique value with arcpy

[Yaron_YosefCohen]

Hi everyone

For disclosure, i asked this question in python - How to remove a specific unique value with arcpy - Geographic Information Systems Stack Exc... but didn't get useful answers.

using arcpy, i would like to remove from 50 mxd files, a specific unique value called "residence a" (exist in 3 layers) from the table of content.

The value of "residence a" is the number  "70"  in the attribute table (in field named "YEUD")

When i use this code:

import arcpy,os,sys
from arcpy import env

env.workspace = r"C:\Project"
for mxdname in arcpy.ListFiles("*.mxd"):
    mxd = arcpy.mapping.MapDocument(r"C:\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 == "residence a":
                print mxdname
                print lyr.name
                print ("1 in layer " + lyr.name)
                arcpy.mapping.RemoveLayer(df, v)        
    mxd.save()
del mxd

i get en error:

>>> Project -.mxd mig1 1 in layer mig1  Traceback (most recent call last): File "C:/Users/yaron.KAYAMOT/Desktop/remove UNIQUE_VALUES in lyr.py", line 18, in    <module> arcpy.mapping.RemoveLayer(df, v) File "C:\Program Files (x86)\ArcGIS\Desktop10.3\ArcPy\arcpy\utils.py", line 182, in fn_ return fn(*args, **kw) File "C:\Program Files (x86)\ArcGIS\Desktop10.3\ArcPy\arcpy\mapping.py", line 1845,     in RemoveLayer assert isinstance(remove_layer, Layer) AssertionError >>> 

I search desperately a solution to my problem -thanks

[DanPatterson_Retired]

the assertion error suggests that it is of the wrong type.  The way you have it set up 'v' is a class in classlabels.  You want to remove the layer apparently which I think is 'lyr' so I suspect if you want to remove the layer if it contains that label, then you should be using  arcpy.mapping.RemoveLayer(df, lyr) .  

[Yaron_YosefCohen]

but i don't want to remove layers mig 1 2 3 .i want to remove only value "residence a",so my TOC will be:

[JakeSkinner]

Hi Y.Y.C,

You can append the unique values to a list, remove the value you do not want to use, and then update the symbology.  Below is an example that removes the value 'Philadelphia International Airport' from a unique value list, and then updates the symbology.  Also, here is a helpful link.

import arcpy
mxd = arcpy.mapping.MapDocument("current")
lyr = arcpy.mapping.ListLayers(mxd, "Airports")[0]
airportList = []
rows = arcpy.da.SearchCursor(lyr, ["NAME"])
for row in rows:
  airportList.append(row[0])

#remove duplicates from list
airportList = dict.fromkeys(airportList)
airportList = airportList.keys()

#remove unique value
airportList.remove('Philadelphia International Airport')

#update symbology
if lyr.symbologyType == "UNIQUE_VALUES":
  lyr.symbology.classValues = airportList
  lyr.symbology.showOtherValues = False

arcpy.RefreshActiveView()
arcpy.RefreshTOC()
del mxd

[Yaron_YosefCohen]

Hi Jake,

in your code you work only with one layer. I want that arcpy will iterate all layers in all 50 mxd's. i have many other layers in the mxd's with different names that including value "residence a" in them.

To your opinion, i must change the layer name every time i want to work on specific layer- this will take a  lot of time

[JakeSkinner]

You would just need to add a 'for' loop for the layers within your MXD.  Ex:

import arcpy  
mxd = arcpy.mapping.MapDocument("current")  
lyrs = arcpy.mapping.ListLayers(mxd, "*")
for layer in lyrs:
  airportList = []  
  rows = arcpy.da.SearchCursor(layer, ["NAME"])  
  for row in rows:  
    airportList.append(row[0])  
    
  #remove duplicates from list  
  airportList = dict.fromkeys(airportList)  
  airportList = airportList.keys()  
    
  #remove unique value  
  airportList.remove('Philadelphia International Airport')  
    
  #update symbology  
  if layer.symbologyType == "UNIQUE_VALUES":  
    layer.symbology.classValues = airportList  
    layer.symbology.showOtherValues = False  
  
arcpy.RefreshActiveView()  
arcpy.RefreshTOC()  
del mxd 

[Yaron_YosefCohen]

Hi Jake,

I tried to build this code (i  also created shp called "Airports" with field "NAME" 😞

import arcpy,os,sys  
from arcpy import env  
  
env.workspace = r"C:\Project\gis"  
for mxdname in arcpy.ListFiles("*.mxd"):  
    mxd = arcpy.mapping.MapDocument(r"C:\Project\gis\\" + mxdname)  
    df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0]  
    lyrs = arcpy.mapping.ListLayers(mxd, "*") 
    for layer in lyrs:
        airportList = []    
        rows = arcpy.da.SearchCursor(layer, ["NAME"])    
        for row in rows:
            airportList.append(row[0])     
        #remove duplicates from list    
        airportList = dict.fromkeys(airportList)    
        airportList = airportList.keys()    
      
        #remove unique value    
        airportList.remove('Philadelphia International Airport')    
      
        #update symbology    
        if layer.symbologyType == "UNIQUE_VALUES":
            layer.symbology.classValues = airportList    
            layer.symbology.showOtherValues = False 

    mxd.save()  
del mxd

but get an error:

>>> ================================ RESTART ================================
=
>>> 


Traceback (most recent call last):
  File "C:\Users\yaron.KAYAMOT\Desktop\python.py", line 19, in <module>
    airportList.remove('Philadelphia International Airport')
ValueError: list.remove(x): x not in list
>>> 

[DanPatterson_Retired]

​it isn't in the list...or is spelled differently always test for existence and return an error warning

to_remove = 'some airport'

if to_remove in airportList:

    airportList.remove(to_remove)

else:

    print "not there bud..."

[Yaron_YosefCohen]

How can i remove 2 unique values?

[DanPatterson_Retired]

removing multiple values from lists gets tricky since the position of values in a list changes as the list gets smaller and smaller.  It is better to regenerate what you want from what you have and don't want.

A small example...and one of many, many, many options is as follows.

• load, compile and run the script below
• change the data and omit variables to experiment
• implement on your own data and data structure

def remove_vals(data,omit):
    as_set = set(data)
    out_lst = [ x for x in data if x not in omit]
    return out_lst

if __name__=="__main__":
    """change below to suit"""
    data = ["a", "d","e","b","c","a","a","a","b","a","c"]
    omit = ["a","e"]
    returned = remove_vals(data,omit)
    frmt = "\nInputs...{}\nTo remove...{}\nOutputs...{}"
    print(frmt.format(data,omit,returned))

The results from the above run are as follows.

>>>
Inputs...['a', 'd', 'e', 'b', 'c', 'a', 'a', 'a', 'b', 'a', 'c']
To remove...['a', 'e']
Outputs...['d', 'b', 'c', 'b', 'c']

Now don't try to copy this code exactly on your problem...emulate and consider what you have, what you want, then go for a solution