Calculate repeating values in field

[JeffBaker2]

Anyone have any ideas how to calculate a field so the values (going down the table) are

1

2

3

1

2

3

1

2

3

etc. to the end of the table?

These values will end up being color codes for rendering.  The actual values will be from 0-9, but need some way to get the repeating values in.  Another option might be to calculate random values instead of repeating values.  Any thoughts?

[DanPatterson_Retired]

If you are running my code... then

seq_num_max(3) ... notice you put the number in not ColorCode... You are calculating ColorCode using ColorCode, not the maximum number that you want

[JamesCrandall]

import arcpy
import pandas

repeat_vals = [1, 2, 3]
df = pandas.DataFrame(range(100), columns=['col1'])
df = df.join(pandas.DataFrame(repeat_vals * (len(df)/len(repeat_vals)+1), columns=['col2']))
print df.values‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

[JamesCrandall]

As an alternative to the field calculator, this is a mix of libraries and ultimately simply uses a dictionary and arcpy.da.UpdateCursor to calculate the field with the repeating values. 

(really, I had been looking for a reason to dive into using a dictionary to update with an UpdateCursor and this was a good exercise to nail that down).

import arcpy
import pandas
import numpy as np
import sys

#set the repeating values to use
repeat_arr = [1, 2, 3]

#the feature class to be updated, the field to calculat and a join field
fc = r'H:\DescribeFGDB\Readme.gdb\RptLyr'
updateField = 'calcIt'
idField = 'OBJECTID'

#convert the feature class to an array with OID values
nparr = arcpy.da.FeatureClassToNumPyArray(fc, ['OID@'])
#get array as pandas dataframe and populate the repeating values column
df = pandas.DataFrame(nparr)
df = df.join(pandas.DataFrame(repeat_arr * (len(df)/len(repeat_arr)+1), columns=['calcIt']))
#convert back to a numpyarry
x = np.array(np.rec.fromrecords(df.values))
names = df.dtypes.index.tolist()
x.dtype.names = tuple(names)

#convert to an in_memory table, set join field and the field to use to calculate with
arcpy.da.NumPyArrayToTable(x, r'in_memory\finalarr')
joinTab = r'in_memory\finalarr'
joinIdField = 'OBJECTID'
joinValueField = 'calcIt'

#create dictionary from the in_memory table
valueDic = dict ([(key, val) for key, val in arcpy.da.SearchCursor(joinTab, [joinIdField,joinValueField])])

#update the source feature class with the dictionary values, joining on the joinfields
with arcpy.da.UpdateCursor(fc, [updateField, idField]) as cursor:
    for update, key in cursor:
        if not key in valueDic:
            continue
        row = (valueDic [key], key)
        cursor.updateRow(row)

del cursor‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍