I am familiar with using the ArcPy Calculate Field tool in Python but was wondering how this is done in a stand alone Python script with a .csv. My ArcPy Snippet looks like this. I assume it's a basic procedure but I couldn't find any previous questions. Feel free to direct me to a similar question.

codeblock = """def Reclass(PA,dist):
                    if PA=="M" and dist==1:
                        return "MM"
                    elif PA=="M" and dist==0:
                         return "MW""""

arcpy.CalculateField_management(fc, field="NEW", expression="Reclass(!Field1!,!Field2!)", expression_type="PYTHON_9.3", code_block=codeblock)
  • I'm a bit confused do you mean how to programmatically run calculate field so that you can access a CSV from outside ArcGIS. For example run Arcpy to access external CSV and bring it into ArcGIS then, perhaps in memory, convert the CSV to a dBASE or geodatabase, run calculate fields and export to CSV?
    – spk578
    Commented Aug 24, 2016 at 13:47
  • Please avoid cross-posting: stackoverflow.com/q/39056544/1446289. More details on SE policy on cross-posting here: meta.stackexchange.com/q/64068
    – Aaron
    Commented Aug 24, 2016 at 14:23

2 Answers 2


It won't work as a CSV is read only. If you want to update your data with field calculations then you need to convert your CSV into a proper data table such as a dBase file or geodatabase table.


You should be able to do this by utilising the scratch workspace and converting your CSV out to a geodatabase table e.g. below

import arcpy, os
#Set path to temp. geodatabase
arcpy.env.scratchWorkspace = r"D:\GIS\database"
#Path to newly created gdb
gdb = arcpy.env.scratchGDB

Then you could use CopyFeatures to add the CSV to the scratch gdb

#Copyfeatures from CSV to gdb
arcpy.CopyFeatures_management(r"c:\temp\foo.csv", gdb)

And from there run the CalculateField tool and export to the scratch gdb using the arcpy.TableToTable_conversion() function.

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