Full compare

[Moi_Nccncc]

I have 2 identical feature class with unique ID, I want to get All IDS from both classes which 
NEW exists in feature  Class 1 not exists in feature Class 2

DELETED exists in feature  Class 2 not exists in feature Class 1

Any ready code?

[AlfredBaldenweck]

Try the feature compare tool?

Just make sure that it doesn’t stop at the first difference and then look at the output table.

https://pro.arcgis.com/en/pro-app/3.1/tool-reference/data-management/feature-compare.htm

Assuming that they have a common identifying field like an ID or name, you could also try joining the two tables on that field and then select by attribute or definition query to meet your criteria.

[Tom_Laue]

To get unique values in a field, I've used.

import arcpy

featureClass = r"C:\Default.gdb\Export_Output_10"
fields = ['FEATUREID']

listOfValues=[]

with arcpy.da.SearchCursor(featureClass, fields) as cursor:
    for row in cursor:
        listOfValues.append(row[0])

Then you can convert the list to a set.

# set() to convert list to set
set_of_values  = set(listOfValues)

Sets can be subtracted from each other to find the differences.

Python Set | difference() - GeeksforGeeks