Updating multiple fields with list values using arcpy.da.UpdateCursor

Question

I have a script that contains a function that fetches XML from a web service, containing a series of metadata values. The function takes a field from a feature class as criteria, queries the web service, and returns a list of metadata values associated with the submitted criteria. My intent is to update various fields in that feature class with these values, and stuff them into a dictionary so I don't have to make more web calls than necessary. I am failing at the point where it is trying to update the fields. Here is the function. It is not efficient, but it works... when I get everything else working, I'll rewrite it using elementree :)

import datetime, time, urllib, sys, arcpy

def getMetadata(id):
    iDate = ''
    iCategory = ''
    iType = ''
    svcURL = r'http://www.someurl.com/?query=" + str(id)
    localFile = r'C:\Temp\localfile.xml'
    urllib.urlretrieve(svcURL, localFile)
    readFile = open(localFile, 'r')
    for line in readFile.readlines():
        if line.find("<date_time>") > -1:
            iDatePre = line[line.find("<date_time>")+11:line.find("</date_time>")]
            iDateObject = datetime.datetime.strptime(iDatePre, '%d-%b-%y %H.%M.%S.%f %p')
            iDate = datetime.datetime.strftime(iDateObject, '%Y-%m-%d %H:%M')
        if line.find("<Category>") > -1:
            iCategory = line[line.find("<Category>")+10:line.find("</Category>")]
        if line.find("<Type>") > -1:
            iType = line[line.find("<Type>")+6:line.find("</Type>")]
        metaData = [iDate, iCategory, iType]
    readFile.close()
    return metaData

So the idea is to use da.UpdateCursor to put those values in a feature class, using row[0] as the function's criteria:

dictOfMetadata = {}

fgdb_name = 'TESTGDB'
fgdb_path = r'C:\Temp'
fgdb = fgdb_path + '\\' + fgdb_name + r'.gdb'
arcpy.env.workspace = fgdb
fdsb = 'dataset_b'

if arcpy.Exists(fdsb):
    print('Found {} dataset.'.format(fdsb))
    fcs = arcpy.ListFeatureClasses('*','',feature_dataset=fdsb)
    for cfc in fcs:
        with arcpy.da.UpdateCursor(cfc, ['ID','DTG','CAT','TYPE']) as cursor:
            for row in cursor:
                idSend = row[0]
                if dictOfMetadata.has_key(idSend):
                    print('Found local metadata for {}.'.format(idSend))
                    cursor.updateRow(row[1, 2, 3] + dictOfMetadata[idSend][0,1,2])
                else:
                    cursor.updateRow(row[1, 2, 3] + getMetadata(idSend)[0, 1, 2])
        del cursor

The error is: TypeError: list indices must be integers, not tuple

I've tried a bunch of different ways to do this but this is the closest I've gotten.

BritishSteel · Accepted Answer · 2016-03-23 15:10:22Z

You are trying to call multiple indices at once, which does not work.

Comma-separated values in Python translate into a tuple, so this:

row[1, 2, 3]

actually translates to this:

row[(1, 2, 3)]

and this is not doable, as you cannot use a tuple as an index. Hence the error message.

Without being able to test this I would suggest the following:

if arcpy.Exists(fdsb):
    print('Found {} dataset.'.format(fdsb))
    fcs = arcpy.ListFeatureClasses('*','',feature_dataset=fdsb)
    for cfc in fcs:
        with arcpy.da.UpdateCursor(cfc, ['ID','DTG','CAT','TYPE']) as cursor:
            for row in cursor:
                idSend = row[0]
                if dictOfMetadata.has_key(idSend):
                    print('Found local metadata for {}.'.format(idSend))
                    row[1] = dictOfMetadata[idSend][0]
                    row[2] = dictOfMetadata[idSend][1]
                    row[3] = dictOfMetadata[idSend][2]
                    cursor.updateRow(row)
                else:
                    row[1] = getMetadata(idSend)[0]
                    row[2] = getMetadata(idSend)[1]
                    row[3] = getMetadata(idSend)[2]
                    cursor.update(row)

You can also omit the del cursor. Deleting a cursor is not necessary as the arcpy.da cursor takes care of this automatically.

If I understood correctly what you are trying to achieve then this should do the job.

Thanks, this does do the job in terms of the row assignments, but how do I get the values back into the dictionary? When I do dictOfMetadata[idSend][0] = row[1] under the else: part of the loop, it gives me a key error... — auslander
– auslander, Commented Mar 23, 2016 at 15:40
Oh, nevermind - I got it, I just did metaData = getMetadata(idSend) in the second loop, and then after I assign the row values I put in dictOfMetadata(idSend) = metaData. Thanks again! — auslander
– auslander, Commented Mar 23, 2016 at 16:03

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