CountIDs.py

'''****************************************************************
CountIDs.py
Author(s): Anders Olson
Usage: Run script using python IDE or similar
Description:
        Script traverses ID field and counts occurrence of each ID
****************************************************************'''

import arcpy
from collections import counter

##~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~##
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# Configure logger
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def outputMessage(msg):
    print(msg)
    arcpy.AddMessage(msg)

def outputError(msg):
    print(msg)
    arcpy.AddError(msg)

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# Define environment and messaging
#================================#
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# Set the overwriteOutput ON
arcpy.gp.overwriteOutput = True

# Set workspace to be in memory for faster run time
arcpy.env.workspace = "in_memory"

outputMessage("Workspace is: {}".format(arcpy.env.workspace))

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#================================#
# Define variables
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#Input shapefile or dbf with id field to count
inData = r"U:\Somedirectory\yourshapefile.shp"

# Empty list for storing all unique IDs
uniqueIDs = []

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#================================#
# Call Functions
#================================#
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# Populate a list of all IDs found in the desired ID field
for row in arcpy.da.SearchCursor(inData, ['<FIELD-NAME>']):
        uniqueIDs.append(row[0])

# Print a list of all ids and no repeating ids i.e. 'keys'
print(Counter(uniqueIDs).keys())

# Print a count for occurrence of each id found in original list i.e. 'values'
print(Counter(uniqueIDs).values())