Variable usage in codeblock

NoahHuntington — Thu, 02 Oct 2014 17:29:07 GMT

I am receiving the error that variable row is not defined (second line of codeblock). I am attempting to check "constraints_Merge_fl" against code value in "lepc_clip_fl". What does the correct usage of this variable in the codeblock look like?

    fc = "lepc_clip"
    code = "CODE"
    field = "OBJECTID"


    # Make fl's for select tools
    arcpy.MakeFeatureLayer_management(fc,fc + "_fl")
    arcpy.MakeFeatureLayer_management("constraints_Merge","constraints_Merge_fl")


    cursor = arcpy.SearchCursor(fc + "_fl")
    row = cursor.next()


    arcpy.AddField_management("constraints_Merge_fl","HEX_ID","Long")


    chat_List = []
    while row:
        code_Value = row.getValue(code)
        hex_ID = row.getValue("Hex_ID")
        chat_List.append(hex_ID)
        for feature in chat_List:
            arcpy.SelectLayerByAttribute_management (fc + "_fl","NEW_SELECTION",'"Hex_ID" = {}' .format(feature))
            arcpy.SelectLayerByLocation_management("constraints_Merge_fl",'intersect', fc + "_fl")
            expression = "getClass(int(!CODE!))"
            # Check syntax for row.getValue(code) in codeblock
            codeblock = """def getClass(code):
                                if code < row.getValue(code):
                                    return row.getValue(code)
                                else:
                                    return code"""
            arcpy.CalculateField_management("constraints_Merge_fl", "CODE", expression, "PYTHON_9.3", codeblock)


        row = cursor.next()

Thanks in advance.

Re: Variable usage in codeblock

JakeSkinner — Thu, 02 Oct 2014 18:55:31 GMT

Hi Noah,

I would recommend using the UpdateCursor to update the field. In my opinion, it's a little easier to code. Also, if you are using 10.1 or above, you can use the arcpy.da.UpdateCursor that is even faster. Below is an example using the UpdateCursor with a data dictionary rather than a list:

fc = "lepc_clip"
code = "CODE"
field = "OBJECTID"

arcpy.MakeFeatureLayer_management(fc,fc + "_fl")
arcpy.MakeFeatureLayer_management("constraints_Merge","constraints_Merge_fl")

chat_List = {}

cursor = arcpy.SearchCursor(fc + "_fl")
for row in cursor:
    code_Value = row.getValue(code)
    hex_ID = row.getValue("Hex_ID")
    chat_List[hex_ID] = code_Value

del row, cursor

for feature in chat_List:
    expression = "Hex_ID = " + str(feature)    
    arcpy.SelectLayerByAttribute_management (fc + "_fl", "NEW_SELECTION", expression)
    arcpy.SelectLayerByLocation_management("constraints_Merge_fl", 'intersect', fc + "_fl")
    cursor = arcpy.UpdateCursor("constraints_Merge_fl")
    for row in cursor:
        if row.Code < chat_List[feature]:
            row.Code = chat_List[feature]
            cursor.updateRow(row)

del row, cursor

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Variable usage in codeblock

Re: Variable usage in codeblock